{,x-pack/}winlogbeat: clean up dead code

[efd6]

What does this PR do?

This removes the majority of unused identified by running:

staticcheck -checks 'U*' ./{,x-pack/}winlogbeat/...

Care has been taken to not remove platform-specific code and mage-required code.

This is the auditbeat part of #30483.

Why is it important?

Deadcode reduces code base maintainability.

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

• The first commit is purely mechanical and can be verified by running git-generate with that commit checked out.
• The second commit should be checked with the view to save deletions from the gallows. I will add lint ignore directives for chunks that are to be retained and revert those chunks.

How to test this PR locally

Related issues

• Relates {,x-pack/}filebeat: clean up dead code #30483.

Use cases

Screenshots

Logs

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Build stats

• Start Time: 2022-02-21T04:21:33.148+0000

• Duration: 134 min 35 sec

Test stats 🧪

Test	Results
Failed	0
Passed	32921
Skipped	3308
Total	36229

💚 Flaky test report

Tests succeeded.

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