Add safe_mode HomeKit (for pairing)

[cdce8p]

Description:

Add safe_mode option to HomeKit component. Setting safe_mode: True will allow pairing even if you previously got stuck after entering the pincode and error msg inside the Home App. With this PR it's no longer necessary to change python files like (old method #14567).

Important No.1: In order to find the Home Assistant Bridge when you have already tried the default before, you need to delete the .homekit.state file inside your config dictionary.

Important No.2: If you unpair the Bridge, you need to restart Home Assistant to start pairing again.

The safe_mode option does only effect pairing and unpairing. Although not recommended, it's safe to leave at True during normal use.

Related issue:
#14567
#17181

This PR requires #18355 to be merged first. The necessary function was added with HAP-python 2.4.0. For testing proposes I've include the commit here as well. I'll do the rebase once the other is merged.

Pull request in home-assistant.io with documentation (if applicable): home-assistant/home-assistant.io#7516

Example entry for configuration.yaml (if applicable):

homekit:
  safe_mode: True

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.io
• Tests have been added to verify that the new code works.

[bverkron]

safe_mode does not seem to be working, for me. Please see issue #19707