Restore __slots__ to core objects

[bdraco]

Proposed change

One of the downsides to using @cached_property is we cannot also use __slots__. With the @under_cached_property we still can because the cache dict is implemented as self._cache instead of using self.__dict__ which __slots__ removed. Since we churn and throw away these objects frequently, the memory and creation time adds up. While the benefit of @cached_property greatly outweighs the benefit of __slots__ its nice to be able to have both.

before

>>> from pympler.asizeof import asizeof
>>> from homeassistant import core
>>> asizeof(core.Context())
640
>>> 

after

>>> from pympler.asizeof import asizeof
>>> from homeassistant import core
>>> asizeof(core.Context())
224
>>> 

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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• The code has been formatted using Ruff (ruff format homeassistant tests)
• Tests have been added to verify that the new code works.

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[bdraco]

FAILED tests/components/reolink/test_init.py::test_new_device_discovered - AssertionError: assert 24 == 0
 +  where 24 = <AsyncMock name='Host().logout' spec='function' id='140036042898656'>.call_count
 +    where <AsyncMock name='Host().logout' spec='function' id='140036042898656'> = <NonCallableMagicMock name='Host()' spec='Host' id='140036030884384'>.logout

test failure is unrelated

[bdraco]

Thanks. Adding them back to the registries will require some more work since they were gone from there longer and mocks are missing some values