Cherry-pick #28868 to 7.17: Enhance add_kubernetes_metadata matcher

[tetianakravchenko]

Cherry-pick of PR #28868 to 7.17 branch. Original message:

Signed-off-by: Tetiana Kravchenko tetiana.kravchenko@elastic.co

What does this PR do?

• add documentation for add_kubernetes_metadata matcher;
• support /var/log/pods/ for resource_type: pod

Why is it important?

to improve understanding on how add_kubernetes_metadata works and which logs_path are supported for available resource_type

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Author's Checklist

• [ ]

How to test this PR locally

Related issues

• closes add_kubernetes_metadata needs to respect logs_path setting #28629

Use cases

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• Start Time: 2022-02-23T08:25:30.558+0000

• Duration: 95 min 17 sec

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Test	Results
Failed	0
Passed	34404
Skipped	3944
Total	38348

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[tetianakravchenko]

/test

[luigibk]

Thanks @tetianakravchenko, will this be released with 7.17.1?