Identify the active ZHA coordinator device in API responses

[puddly]

Breaking change

No.

Proposed change

Users who switch coordinators but keep their zigbee.db will be stuck with a stale coordinator entry for their old hardware that cannot be deleted from the frontend.

This change adds the necessary key to the device API response for the frontend to distinguish between the currently coordinator and old coordinators.

I've also added myself as a ZHA code owner.

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 #
• 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.
• For the updated dependencies - a link to the changelog, or at minimum a diff between library versions is added to the PR description.
• Untested files have been added to .coveragerc.

The integration reached or maintains the following Integration Quality Scale:

• No score or internal
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To help with the load of incoming pull requests:

• I have reviewed two other open pull requests in this repository.

[probot-home-assistant]

Hey there @dmulcahey, @Adminiuga, mind taking a look at this pull request as it has been labeled with an integration (zha) you are listed as a code owner for? Thanks!
_{^{(message by CodeOwnersMention)}}

[puddly]

Looks like the frontend PR got merged first (home-assistant/frontend#13154). This one's ready to go too.