have climate fallback to state if no ATTR_OPERATION_MODE (#12272)

[ttroy50]

Description:

As described in #12272 if a cliate device doesn't support setting operation mode, the google assistant component will not return the state of the device.

This updates google assistant to fallback to using the state if the operation_mode attribute is not available.

Related issue (if applicable): fixes #12272

Checklist:

• The code change is tested and works locally.

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

• Documentation added/updated in home-assistant.github.io

If the code communicates with devices, web services, or third-party tools:

• Local tests with tox run successfully. Your PR cannot be merged unless tests pass
• New dependencies have been added to the REQUIREMENTS variable (example).
• New dependencies are only imported inside functions that use them (example).
• New dependencies have been added to requirements_all.txt by running script/gen_requirements_all.py.
• New files were added to .coveragerc.

If the code does not interact with devices:

• Local tests with tox run successfully. Your PR cannot be merged unless tests pass
• Tests have been added to verify that the new code works.

[balloob]

State is almost always equal to operation mode (source). Better to just point Google Assistant at the state instead of doing an if…else.

[ttroy50]

@balloob I considered just returning state but thought that the check of is_on might change some existing components so didn't want to risk that.

You could avoid the if .. else if I rewrote it as mode = entity.attributes.get(climate.ATTR_OPERATION_MODE, entity.state).lower() but I personally prefer the more explicit if .. else