Add group entity support to ZHA

[dmulcahey]

Proposed change

This PR adds entities for ZHA groups. Starting with this PR if a ZHA Zigbee group contains 2 or members with entities of the same type (in this case lights) we will create an entity to represent the group. This allows us to abstract away all of the work that a user currently has to do in an automation to interact with groups and also provides a single point of contact on the UI (think light group entities) that will allow them to naturally interact with groups of devices. I am planning to follow up this PR with several others to expand the support. Fan, Cover, and Switch will get support next followed by a feature that will give users the ability to override the default chosen entity domain for the group in the ZHA config panel.

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 #
• 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.

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[probot-home-assistant]

Hey there @Adminiuga, mind taking a look at this pull request as its been labeled with a integration (zha) you are listed as a codeowner for? Thanks!

[Adminiuga]

Overall looks good