Lambda instrumentation

[AlexanderWert]

What does this PR do?

Closes #1911

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

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💚 Build Succeeded

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• Start Time: 2021-11-30T16:01:51.880+0000

• Duration: 69 min 48 sec

• Commit: 546344e

Test stats 🧪

Test	Results
Failed	0
Passed	2617
Skipped	21
Total	2638

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Tests succeeded.

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[AlexanderWert]

@eyalkoren Your changes LGTM!

[eyalkoren]

Tested manually:

1. all handler types, with the matching event type and with a non-matching event type
2. both options of handle method specification - package.Handler vs package.Handler::handleRequest
3. metadata
4. transaction context and name
5. some special configurations (e.g. log_level and trace_methods)

Documents were added as well, and an additional release step (not automated atm as it is probably only temporary).

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❕ Build Aborted

There is a new build on-going so the previous on-going builds have been aborted.

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• Reason: Aborted from #133

• Start Time: 2021-12-01T12:26:12.321+0000

• Duration: 32 min 46 sec

• Commit: f776ad9

Test stats 🧪

Test	Results
Failed	0
Passed	1794
Skipped	9
Total	1803

🤖 GitHub comments

To re-run your PR in the CI, just comment with:

• /test : Re-trigger the build.

• run benchmark tests : Run the benchmark test.

• run compatibility tests : Run the JDK Compatibility test.

• run integration tests : Run the APM-ITs.

• run elasticsearch-ci/docs : Re-trigger the docs validation. (use unformatted text in the comment!)