Cherry-pick #24535 to 7.x: Move logging defaults to agent

[michalpristas]

Cherry-pick of PR #24535 to 7.12 branch. Original message:

What does this PR do?

In #24466 i introduced default in libbeat and this PR moves it to agent so other beats are not affected by agent requirements.

Why is it important?

Separation

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.

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Pinging @elastic/agent (Team:Agent)

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Pinging @elastic/ingest-management (Team:Ingest Management)

[elasticmachine]

💚 Build Succeeded

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Build stats

• Build Cause: Pull request #24539 opened

• Start Time: 2021-03-15T13:20:56.827+0000

• Duration: 107 min 18 sec

• Commit: 62ffd40

Test stats 🧪

Test	Results
Failed	0
Passed	45560
Skipped	5139
Total	50699

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Test stats 🧪

Test	Results
Failed	0
Passed	45560
Skipped	5139
Total	50699