Add Supervisor discovery to motionEye

[frenck]

Proposed change

Add Supervisor discovery of the motionEye integration, when an add-on is installed that provides motionEye.

Supervisor support was added in home-assistant/supervisor#2850 and is currently in dev/beta to go for stable before Core 2021.6 ships.

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

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.

The integration reached or maintains the following Integration Quality Scale:

• No score or internal
• 🥈 Silver
• 🥇 Gold
• 🏆 Platinum

To help with the load of incoming pull requests:

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

[frenck]

Rebased this PR onto the latest dev. I can now start doing a full end-2-end test, so I can get this PR ready for review/merge.

[frenck]

The discovered integration instance is not ignorable, this is a bug in the frontend. Tests have been included to show it works from the backend.

[frenck]

Works as expected ✅ Marking PR ready for review/merge.

[frenck]

Needs #50965 to fix CI.

[dermotduffy]

[Besides the failing CI] This looks great, one minor comment added. Thank you for working on this!

[frenck]

• Rebased to fix CI
• Adjusted config entry title

[frenck]

Rebased onto the latest dev, in order to make the tests pass.