Migrate restore_state helper to use registry loading pattern

[bdraco]

Its been a while since I looked at startup performance. The new yellow got me looking at it again since when I migrated my production config to it, I noticed a few integrations failed at startup (and had to retry) because the cpu load got too high during startup.

Proposed change

As more entities have started using restore_state over time, it has become a startup bottleneck as each entity being added is creating tasks (was using a gather) to load restore state data that is already loaded since it is a singleton

We now use the same pattern as the registry helpers

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

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• This PR fixes or closes issue: fixes #
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[bdraco]

This one is interesting since it looks like some race bugs might be relying on the gather that was previously here.

Was a refactoring error 🤦

[bdraco]

add_to_platform_finish looks a lot better now along with the automation bound method change.

Will likely need to adjust some mocks

[bdraco]

It seems like setting update_before_add=True when its not needed is more common than I expected. Will need to audit for that

[bdraco]

Missing coverage is existing. Code is only moved that if affected and not changed

[bdraco]

Thanks. Thats the bulk of the startup improvements. Going to work with Mike on the numerous hassio get requests at startup next cycle