Support reloading the rest notify platform

[bdraco]

Requires #39511

WTH: https://community.home-assistant.io/t/why-the-heck-is-a-restart-needed-for-each-an-every-change-to-configuration-yaml/219630/10?u=bdraco

Frontend PR: home-assistant/frontend#6759

Proposed change

Support reloading the rest notify platform

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)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Example entry for configuration.yaml:

# Example configuration.yaml

Additional information

• This PR fixes or closes issue: fixes #
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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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