Generate switches for harmony activities automatically (#42331)

* Adding switch code for harmony activities

* Working on-off

* Removing poll code for now

* Async updates for current activity

* Update our state based on events

* Notifications we got connected or disconnected

* Remove unncessary constructor arg

* Initial switch tests

* Additional tests for switch transitions

* Test transitions for availability

* Testing switch state changes

* Tests passing

* Final tests

* Updating manifest.

* Correctly mock the return value from a call to the library

* Adding new subscriber classes

* Update class name and location

* Got the refactor working locally.

* Tests passing

* Tracking state changes

* Remove write_to_config_file - this appears to never be read.

It was added far back in the past to account for a harmony library
change, but nothing ever reads that path.

Removing that side effect from tests is a pain - avoid the side effect
completely.

* Connection changes tested

* Clean up temporary code

* Update .coveragerc for harmony component

Specifically exclude untested files instead of the whole module

* Fix linting

* test sending activity change commands by id

* Improving coverage

* Testing channel change commands

* Splitting subscriber logic into it's own class

* Improve coverage and tighten up .coveragerc

* Test cleanups.

* re-add config file writing for harmony remote

* Create fixture for the mock harmonyclient

* Reduce duplication in subscription callbacks

* use async_run_job to call callbacks

* Adding some tests for async behaviors with subscribers.

* async_call_later for delay in marking remote unavailable

* Test disconnection handling in harmony remote

* Early exit if activity not specified

* Use connection state mixin

* Lint fix after rebase

* Fix isort

* super init for ConnectionStateMixin

* Adding @mkeesey to harmony CODEOWNERS