Hide "Browse Media" button for unavailable media players

[spacegaier]

Breaking change

Proposed change

Hide the button if the entity is not available. The same is already done for the UI elements such as source selection, volume buttons, ... if the media player is not available.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature (thank you!)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Example configuration

Additional information

• This PR fixes or closes issue: fixes Media Browser button not disabled on unavailable media players in more info dialog #20531
• This PR is related to issue or discussion:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• 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