Use Implementation-Version as default service version if it is available

[tobiasstadler]

What does this PR do?

When the MANIFEST.MF of main jar contains the Implementation-Version attribute, it is used as the default service version (except for application servers).

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

[ghost]

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• Reason: null

• Start Time: 2022-01-26T16:49:55.428+0000

• Duration: 54 min 10 sec

• Commit: 141e256

Test stats 🧪

Test	Results
Failed	0
Passed	2449
Skipped	16
Total	2465

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[tobiasstadler]

Could someone please have a look?

[tobiasstadler]

@SylvainJuge Maybe you can spare some time please

[tobiasstadler]

@felixbarny Maybe you can spare some time please?

[SylvainJuge]

Hi @tobiasstadler, we have added this to our short-term backlog.
While we can't provide guarantees nor ETA, we will try to handle it soon.

[tobiasstadler]

Thank You! I am looking forward to it.

[tobiasstadler]

Any chance this will make it into 1.29.0?

[felixbarny]

Good improvement and fits will with the just merged implementation-title detection. Let's refactor the code a bit and I think we're good to go.

[felixbarny]

Sorry, I meant to request changes instead of approving.

[tobiasstadler]

/elasticsearch-ci/docs

[felixbarny]

I took the liberty to push some polishing changes

[felixbarny]

run elasticsearch-ci/docs

[tobiasstadler]

@felixbarny Would you please run elasticsearch-ci/docs again?

[felixbarny]

run elasticsearch-ci/docs

[tobiasstadler]

Thank You!