Force color or white mode exclusivity for MQTT lights

[emontnemery]

Breaking change

Home Assistant internally assumes that a light either has a color or a color temperature.
MQTT lights, basic schema, with support for both color and color temperature will report a color if white_value is 0 or None and a color_temp is white_value > 0.

By enforcing this, setting scenes for MQTT lights with basic schema supporting both color temperature and color will now work.

Starting with HA 0.118, an

Proposed change

Force color or white mode exclusivity for MQTT lights using basic schema to prevent ambiguous states which can't be restored.
This affects RGBW and RGBWW lights.

Implemented by interpreting white_value as a selector between color mode or white mode:

• white_value undefined or 0

  • light is in color mode
  • white_value and color_temperature will not be included in state
  • hs_color will be included in state

• white_value > 0

  • light is in white mode
  • white_value and color_temperature will be included in state
  • hs_color will not be included in state

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

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• This PR fixes or closes issue: fixes #
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[probot-home-assistant]

Hey there @home-assistant/core, mind taking a look at this pull request as its been labeled with an integration (mqtt) you are listed as a codeowner for? Thanks!
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