[8.0] processor/otel: clone shared labels for log events (backport #7358)

[mergify]

This is an automatic backport of pull request #7358 done by Mergify.
Cherry-pick of afdd45e has failed:

On branch mergify/bp/8.0/pr-7358
Your branch is up to date with 'origin/8.0'.

You are currently cherry-picking commit afdd45ef.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   processor/otel/logs.go

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   changelogs/head.asciidoc
	both modified:   processor/otel/logs_test.go

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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• Start Time: 2022-02-21T12:45:41.309+0000

• Duration: 62 min 59 sec

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Passed	5629
Skipped	20
Total	5649

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