Add overload for async singleton call with HassKey

[cdce8p]

Proposed change

This PR adds another overload for singleton to support decorating async functions with HassKey as data_key. AFAICT this would especially be useful for esphome (done in this PR) and assist_pipeline which I'd do in a followup.

For type checkers to be able to differentiate the overload definitions, a dummy argument async_ is added.

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 #
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• Tests have been added to verify that the new code works.

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[home-assistant]

Hey there @OttoWinter, @jesserockz, @kbx81, @bdraco, mind taking a look at this pull request as it has been labeled with an integration (esphome) you are listed as a code owner for? Thanks!

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[gjohansson-ST]

I suppose this should go into a test file in tests instead

[cdce8p]

The test files aren't type checked. At some point, it might make sense to have a separate test suite for type tests as there are one or two more files these tests but I don't think it's necessary just yet.

One of the other cases:

core/homeassistant/util/hass_dict.pyi

Lines 99 to 104 in 4023409

	def _test_hass_dict_typing() -> None: # noqa: PYI048
	"""Test HassDict overloads work as intended.
	This is tested during the mypy run. Do not move it to 'tests'!
	"""
	d = HassDict()

[home-assistant]

Please take a look at the requested changes, and use the Ready for review button when you are done, thanks 👍

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