Remove rainbird yaml config test fixtures

[allenporter]

Proposed change

Remove test fixtures related to testing rainbird yaml that were removed from #92599 and simplify the overall test fixture setup, removing the need for some generators (except in one case that handles an override).

Tackling this before #101603 to simplify the scope of that PR.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
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• Tests have been added to verify that the new code works.

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[home-assistant]

Hey there @konikvranik, mind taking a look at this pull request as it has been labeled with an integration (rainbird) you are listed as a code owner for? Thanks!

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[frenck]

Love the 🧹 Thanks @allenporter 👍

../Frenck

[frenck]

Tagged this little cleanup for 2023.11.3, as it resolves a conflict with #101603