Remove evohome hvac_action as it is inaccurate

[zxdavb]

Breaking change

The hvac_action() property has been removed from Evohome zones as this data was clearly inaccurate - the algorithm used to provide this data was not reliable, and there is no reasonable hope for a satisfactory alternative.

The user will have no indication if a zone is actively calling for heat (CURRENT_HVAC_*), nor if the heat source is currently active. However, they will continue to have the hvac_mode() property, which will indicate if the heating is enabled, or not (HVAC_MODE_*).

This will be most obvious to the end user by the absence of this information in the UI. A detailed explanation, with a specific example can be seen in #29559.

This is a breaking change, and there is no intervention required from the end-user.

Proposed change

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 evohome hvac_action() (active / call for heat) is inaccurate #29559
• This PR is related to issue:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist
• The code has been formatted using Black (black --fast homeassistant tests)
• Tests have been added to verify that the new code works.

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

• Documentation added/updated for www.home-assistant.io

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

• The manifest file has all fields filled out correctly.
  Updated and included derived files by running: python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt.
  Updated by running python3 -m script.gen_requirements_all.
• Untested files have been added to .coveragerc.

The integration reached or maintains the following Integration Quality Scale:

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[KTibow]

Random thing @zxdavb: you can mark a PR as a draft instead of putting "WIP" in there.

[zxdavb]

Yeah - I'm a bit rusty & I forgot!

[zxdavb]

@MartinHjelmare A small/simple PR, but as a breaking change, would you please cast an eye over it for me?