Improve Homekit media_player options

[cdce8p]

Description:

The goal of this PR is to replace the entity_config mode option for media_player entities with the feature_list. Since the media_player #14446 isn't yet merged into rc or master this would not technical be a breaking change. Using the proposed config allows for more flexibility down the road, has more resemblance to the platform config logic and thus will probably be a bit easier to understand.

The config change aside, homekit will not add all supported features for media_players anymore by default, since in most cases added four separate switches for on / off, play / pause, play / stop, mute / unmute insn't desired.

Pull request in home-assistant.github.io with documentation (if applicable): home-assistant/home-assistant.io#5447

Example entry for configuration.yaml (if applicable):

# Current version to add support for media_player modes
homekit:
  entity_config:
    media_player.bedroom:
      name: Player  # Other value (not changed)
      mode:
        - on_off
        - toggle_mute

# Proposed solution
homekit:
  entity_config:
    media_player.bedroom:
      name: Player  # Other value (not changed)
      feature_list:
        - feature: on_off
          name: On / Off   # Not yet implemented
          # Additional parameter for each feature can be inserted here.
        - feature: toggle_mute

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass
• Documentation added/updated in home-assistant.github.io
• Tests have been added to verify that the new code works.

CC: @schmittx