feat: IPFS_WAIT_REPO_LOCK (#10797)

* repo: optionally wait to acquire repo lock

Retry acquiring repo lock for a specified amount of time. Retry once per second until time is expired ro lock is acquired.

Lock wait timeout is specified using the environment variable `IPFS_WAIT_REPO_LOCK` and assigning it a value that is parsable as a golang `time.Duration`. For example:

```
IPFS_WAIT_REPO_LOCK="5s"
```

Closes #10482

* document IPFS_WAIT_REPO_LOCK

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Co-authored-by: Marcin Rataj <lidel@lidel.org>