[7.x] translate otel messaging.* to ecs (backport #5334)

[mergify]

This is an automatic backport of pull request #5334 done by Mergify.
Cherry-pick of 16618f2 has failed:

On branch mergify/bp/7.x/pr-5334
Your branch is up to date with 'origin/7.x'.

You are currently cherry-picking commit 16618f2a.
  (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/consumer.go
	modified:   processor/otel/consumer_test.go

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

To fix up this pull request, you can check it out locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

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[apmmachine]

💚 Build Succeeded

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Build stats

• Build Cause: Pull request #5375 updated

• Start Time: 2021-05-31T12:45:37.967+0000

• Duration: 43 min 47 sec

• Commit: 1313b37

Test stats 🧪

Test	Results
Failed	0
Passed	4706
Skipped	121
Total	4827

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