[9.2] (backport #10537) Fix tests in preparation for making otel self monitoring default

[mergify]

What does this PR do?

Fixes tests which implicitly assume beats are running as processes as opposed to otel receivers. More specifically:

• 2952a12 makes the runtime leak test only look at beats running as processes.
• c0d8385 makes integration tests check for running agent processes by only looking at processes without parents which are also elastic agents.
• 72855e5 explicitly sets the runtime in tests where it matters.
• 9d8cc7a checks for beats metrics in a more generic way.
• 1c1a0c3 checks for the component build hash in a way that covers beats receivers as well.

Why is it important?

We want to enable beats receivers for self-monitoring by default. This PR makes the test adjustments separately to show they all pass for beats processes as well.

Checklist

• I have read and understood the pull request guidelines of this project.
• 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/fragments using the changelog tool
• I have added an integration test or an E2E test

Related issues

• Relates [beats receivers] Enable beats receivers for internal monitoring data collection by default #9058

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This is an automatic backport of pull request #10537 done by [Mergify](https://mergify.com).