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Fixes: #11272

This ensures that all the prometheus monitoring and usage
trackers to avoid alerts configured, although we cannot
support v1 to v2 here - we can v2 to v3.

fixes #11265

When the file name or the prefix contains `#`,
whatever comes after is ingored.

This is fixed by encoding the object path using
encodeURIComponent.

Fixes #11112

- for large objects we found that 1MiB block for
  r/w respectively.
- for small objects we found that 128KiB block for
  r/w respectively.

A lot of memory is consumed when uploading small files in parallel, use
the default upload parameters and add MINIO_AZURE_UPLOAD_CONCURRENCY for
users to tweak.

Synchronous replication can be enabled by setting the --sync
flag while adding a remote replication target.

This PR also adds proxying on GET/HEAD to another node in a
active-active replication setup in the event of a 404 on the current node.

another optimization is renameLegacyMetadata() never needs
to validate bucket with os.Stat() again, leading to reduction
in one extra syscall.

As per https://stackoverflow.com/a/3758443/8156177, OpenSSL expects a certificate via STDIN. 
`-new` will allow a new certificate to be generated instead.

Review for missing Close of returned value from `GetObjectNInfo`.

This was often obscured by the stuff that auto-unlocks when reaching EOF.

This PR refactors the way we use buffers for O_DIRECT and
to re-use those buffers for messagepack reader writer.

After some extensive benchmarking found that not all objects
have this benefit, and only objects smaller than 64KiB see
this benefit overall.

Benefits are seen from almost all objects from

1KiB - 32KiB

Beyond this no objects see benefit with bulk call approach
as the latency of bytes sent over the wire v/s streaming
content directly from disk negate each other with no
remarkable benefits.

All other optimizations include reuse of msgp.Reader,
msgp.Writer using sync.Pool's for all internode calls.

fixes #11246

30 seconds white spaces is long for some setups which time out when no
read activity in short time, reduce the subnet health white space ticker
to 5 seconds, since it has no cost at all.

Use separate sync.Pool for writes/reads

Avoid passing buffers for io.CopyBuffer()
if the writer or reader implement io.WriteTo or io.ReadFrom
respectively then its useless for sync.Pool to allocate
buffers on its own since that will be completely ignored
by the io.CopyBuffer Go implementation.

Improve this wherever we see this to be optimal.

This allows us to be more efficient on memory usage.
```
   385  // copyBuffer is the actual implementation of Copy and CopyBuffer.
   386  // if buf is nil, one is allocated.
   387  func copyBuffer(dst Writer, src Reader, buf []byte) (written int64, err error) {
   388  	// If the reader has a WriteTo method, use it to do the copy.
   389  	// Avoids an allocation and a copy.
   390  	if wt, ok := src.(WriterTo); ok {
   391  		return wt.WriteTo(dst)
   392  	}
   393  	// Similarly, if the writer has a ReadFrom method, use it to do the copy.
   394  	if rt, ok := dst.(ReaderFrom); ok {
   395  		return rt.ReadFrom(src)
   396  	}
```

From readahead package
```
// WriteTo writes data to w until there's no more data to write or when an error occurs.
// The return value n is the number of bytes written.
// Any error encountered during the write is also returned.
func (a *reader) WriteTo(w io.Writer) (n int64, err error) {
	if a.err != nil {
		return 0, a.err
	}
	n = 0
	for {
		err = a.fill()
		if err != nil {
			return n, err
		}
		n2, err := w.Write(a.cur.buffer())
		a.cur.inc(n2)
		n += int64(n2)
		if err != nil {
			return n, err
		}
```

* Add Optimization as a type of change. 
* Make the checkmark affirmative instead of disaffirming

fixes: #11180

fixes #11209

CI tests could trigger a data race.

Servers are generally not expected to reinitialize, so tests could trigger data races when reinitializing and async operations are running.

We add the option to safely reset global vars instead of overwriting.

Fixes races like:

```
WARNING: DATA RACE
Read at 0x00000477ab18 by goroutine 1159:
  github.com/minio/minio/cmd.FileInfo.ToObjectInfo()
      /home/runner/work/minio/minio/cmd/erasure-metadata.go:105 +0x16d
  github.com/minio/minio/cmd.erasureObjects.putObject()
      /home/runner/work/minio/minio/cmd/erasure-object.go:748 +0x13f8
  github.com/minio/minio/cmd.(*erasureObjects).listPath.func3.2()
      /home/runner/work/minio/minio/cmd/metacache-set.go:682 +0x7d3
  github.com/minio/minio/cmd.newMetacacheBlockWriter.func1.2()
      /home/runner/work/minio/minio/cmd/metacache-stream.go:777 +0x1c4
  github.com/minio/minio/cmd.newMetacacheBlockWriter.func1()
      /home/runner/work/minio/minio/cmd/metacache-stream.go:806 +0x614

Previous write at 0x00000477ab18 by goroutine 1269:
  [failed to restore the stack]

Goroutine 1159 (running) created at:
  github.com/minio/minio/cmd.newMetacacheBlockWriter()
      /home/runner/work/minio/minio/cmd/metacache-stream.go:760 +0x112
  github.com/minio/minio/cmd.(*erasureObjects).listPath.func3()
      /home/runner/work/minio/minio/cmd/metacache-set.go:672 +0xe22

Goroutine 1269 (running) created at:
  testing.(*T).Run()
      /opt/hostedtoolcache/go/1.14.13/x64/src/testing/testing.go:1095 +0x537
  testing.runTests.func1()
      /opt/hostedtoolcache/go/1.14.13/x64/src/testing/testing.go:1339 +0xa6
  testing.tRunner()
      /opt/hostedtoolcache/go/1.14.13/x64/src/testing/testing.go:1050 +0x1eb
  testing.runTests()
      /opt/hostedtoolcache/go/1.14.13/x64/src/testing/testing.go:1337 +0x594
  testing.(*M).Run()
      /opt/hostedtoolcache/go/1.14.13/x64/src/testing/testing.go:1252 +0x2ff
  github.com/minio/minio/cmd.TestMain()
      /home/runner/work/minio/minio/cmd/test-utils_test.go:120 +0x44e
  main.main()
      _testmain.go:1408 +0x223
==================
==================
WARNING: DATA RACE
Read at 0x00000477aae8 by goroutine 1159:
  github.com/minio/minio/cmd.(*BucketVersioningSys).Enabled()
      /home/runner/work/minio/minio/cmd/bucket-versioning.go:26 +0x52
  github.com/minio/minio/cmd.FileInfo.ToObjectInfo()
      /home/runner/work/minio/minio/cmd/erasure-metadata.go:105 +0x197
  github.com/minio/minio/cmd.erasureObjects.putObject()
      /home/runner/work/minio/minio/cmd/erasure-object.go:748 +0x13f8
  github.com/minio/minio/cmd.(*erasureObjects).listPath.func3.2()
      /home/runner/work/minio/minio/cmd/metacache-set.go:682 +0x7d3
  github.com/minio/minio/cmd.newMetacacheBlockWriter.func1.2()
      /home/runner/work/minio/minio/cmd/metacache-stream.go:777 +0x1c4
  github.com/minio/minio/cmd.newMetacacheBlockWriter.func1()
      /home/runner/work/minio/minio/cmd/metacache-stream.go:806 +0x614

Previous write at 0x00000477aae8 by goroutine 1269:
  [failed to restore the stack]

Goroutine 1159 (running) created at:
  github.com/minio/minio/cmd.newMetacacheBlockWriter()
      /home/runner/work/minio/minio/cmd/metacache-stream.go:760 +0x112
  github.com/minio/minio/cmd.(*erasureObjects).listPath.func3()
      /home/runner/work/minio/minio/cmd/metacache-set.go:672 +0xe22

Goroutine 1269 (running) created at:
  testing.(*T).Run()
      /opt/hostedtoolcache/go/1.14.13/x64/src/testing/testing.go:1095 +0x537
  testing.runTests.func1()
      /opt/hostedtoolcache/go/1.14.13/x64/src/testing/testing.go:1339 +0xa6
  testing.tRunner()
      /opt/hostedtoolcache/go/1.14.13/x64/src/testing/testing.go:1050 +0x1eb
  testing.runTests()
      /opt/hostedtoolcache/go/1.14.13/x64/src/testing/testing.go:1337 +0x594
  testing.(*M).Run()
      /opt/hostedtoolcache/go/1.14.13/x64/src/testing/testing.go:1252 +0x2ff
  github.com/minio/minio/cmd.TestMain()
      /home/runner/work/minio/minio/cmd/test-utils_test.go:120 +0x44e
  main.main()
      _testmain.go:1408 +0x223
==================
```

without this change, there is a performance
regression for small objects GETs, this makes
the overall speed to go back to pre '59d363'
commit days.

with changes present to automatically throttle crawler
at runtime, there is no need to have an environment
value to disable crawling. crawling is a fundamental
piece for healing, lifecycle and many other features
there is no good reason anyone would need to disable
this on a production system.

* Apply suggestions from code review

fixes #11196