Introduce first strategic provider: do nothing

core/builder.go

core/commands/bitswap.go

core/core.go

core/coreapi/coreapi.go

core/node/core.go

core/node/groups.go

core/node/provider.go

go.mod

go.sum

provider/offline.go

provider/provider.go

provider/queue/queue.go

provider/queue/queue_test.go

provider/simple/provider.go

provider/simple/provider_test.go

provider/simple/reprovide.go

provider/simple/reprovide_test.go

provider/system.go

reprovide/providers.go

test/sharness/lib/iptb-lib.sh