Fix for Google Calendar API returning invalid RRULE:DATE rules

[allenporter]

Proposed change

Fix and test for Google Calendar API returning invalid rules that don't match the rfc5545 expectations. There are a couple problems going on here:

• First, the client library gcal_sync coerces the RRULE;DATE to be RDATE ("DATE" in an RRULE is not a thing). The initial fix didn't work and the fix in 6.0.1 actually works this time fixed in Bump gcal_sync to 6.0.1 #103861.
• Second, google integration has a bug where lstrip of RRULE was used where removeprefix was more appropriate. The result is that RDATE was converted to DATE since R is in RRULE. This check has been modified.
• Third, google now only passes up RRULE rules (ignoring RDATE or EXDATE rules which are not supported by the Home Assistant frontend). These continue to be treated as flattened event instances, rather than as part of a series.

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 Error fetching Google Calendar data: Invalid recurrence rule in 2023.04.2 #91119
• This PR is related to issue:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist
• I have followed the perfect PR recommendations
• The code has been formatted using Black (black --fast homeassistant tests)
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

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  Updated and included derived files by running: python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt.
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• Untested files have been added to .coveragerc.

To help with the load of incoming pull requests:

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[balloob]

Thanks!

Should this go to a milestone?

[allenporter]

Thanks!

Should this go to a milestone?

Done. Also tagged #103861 which is a pre-req.