Add Audio Output sensors, rename Microphone to Audio Input

[zacwest]

Fixes #1958.

Summary

Existing Core Audio stuff already exposes the output devices pretty easily, so creating sensors from 'em is pretty easy.

Sensor Values

Roughly identical to microphones:

Sensor	Attributes	Description
sensor.active_audio_input	All, Active	The name of the active audio input (microphone), or Inactive if not in use.
sensor.active_audio_output	All, Active	The name of the active audio output (speaker), or Inactive if not in use.
binary_sensor.audio_input_in_use	None	Whether an audio output (microphone) on the system is currently in use.
binary_sensor.audio_output_in_use	None	Whether an audio output (speaker) on the system is currently in use.

Link to pull request in Documentation repository

Documentation: home-assistant/companion.home-assistant#627

Any other notes

This updates relatively instantly for when output starts, but takes a few seconds before it updates once output pauses.

Existing microphone sensors won't have their unique IDs changed, but their display name will change. New installs will get the new unique ID.

[codecov]

Codecov Report

Merging #1978 (888d626) into master (e788cfe) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1978   +/-   ##
=======================================
  Coverage   29.01%   29.01%           
=======================================
  Files         268      268           
  Lines       20956    20957    +1     
=======================================
+ Hits         6080     6081    +1     
  Misses      14876    14876           

Impacted Files	Coverage Δ
.../API/Webhook/Sensors/InputOutputDeviceSensor.swift	69.23% <100.00%> (ø)
Sources/Shared/Environment/Environment.swift	66.97% <100.00%> (ø)

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