Track metrics for each service individually (#2204)

[tobiasstadler]

What does this PR do?

Fixes #2204

Checklist

• This is an enhancement of existing features, or a new feature in existing plugins
  • I have updated CHANGELOG.asciidoc
  • I have added tests that prove my fix is effective or that my feature works
  • Added an API method or config option? Document in which version this will be introduced
  • I have made corresponding changes to the documentation

[tobiasstadler]

The necessary changes in the apm server can be found in elastic/apm-server#6407

[apmmachine]

💚 Build Succeeded

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Build stats

• Start Time: 2021-10-26T12:37:17.513+0000

• Duration: 68 min 37 sec

• Commit: c93f178

Test stats 🧪

Test	Results
Failed	0
Passed	2476
Skipped	19
Total	2495

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Tests succeeded.

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[felixbarny]

/test

[felixbarny]

@elasticmachine run elasticsearch-ci/docs

[jackshirazi]

/test

[tobiasstadler]

Thank You!