Implement Logitech Media Server in mainsteam AmpliPi

[rtertiaer]

Filing this as a draft for now. When completed, this ought to close #532 . I'd like some early feedback because we'd like to ship 0.3.0 before the holidays.

[codecov-commenter]

Codecov Report

Attention: 35 lines in your changes are missing coverage. Please review.

Comparison is base (725ccf0) 51.52% compared to head (0d470f2) 51.52%.

Files	Patch %	Lines
amplipi/app.py	18.18%	18 Missing ⚠️
amplipi/streams.py	0.00%	9 Missing ⚠️
amplipi/ctrl.py	83.33%	4 Missing ⚠️
amplipi/defaults.py	86.95%	3 Missing ⚠️
tests/test_rest.py	75.00%	1 Missing ⚠️

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Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #549      +/-   ##
===========================================
- Coverage    51.52%   51.52%   -0.01%     
===========================================
  Files           23       24       +1     
  Lines         5624     5673      +49     
===========================================
+ Hits          2898     2923      +25     
- Misses        2726     2750      +24     

Flag	Coverage Δ
unittests	51.52% <58.82%> (-0.01%)	⬇️

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[rtertiaer]

per in-person review:

• remove deallocatable stuff - PersistentStreams class does most or all of what we want
• Make the LMS mode frontend stuff a toggle-able switch, with state
• ensure in LMS mode, streams are eagerly started/activate()d instead of lazily (when finally attached to a source)

[rtertiaer]

I considered doing this in the constructor but the controller is the bit that knows & cares about if it's in LMS mode.

[linknum23]

Testing this on lamplipi shows the lms clients dropping after a reset. Heres the sequence I tested.

1. Enable LMS mode
2. Set each source to its corresponding RCA input
3. Went to config->reset
4. All LMS clients are missing now from the LMS Server UI hosted on port 9000

[rtertiaer]

@linknum23 I was not able to replicate your problem above. I'd love to hash this out a smidge in person, because there's some wackiness with our multiple test beds that I think is complicating things a little bit.

[rtertiaer]

@linknum23 I think the thing you bumped into is fixed now. The bug was that every other restart of squeezelite leaves the ALSA loopback in a funny state and it cannot properly bind to the 'device'; it then simply bails with an error. The fix ultimately required us building our own squeezelite .deb for an upstream commit, which permitted us to manage squeezelite using process_monitor.py.

I'm going to continue testing this.

[linknum23]

This PR really needs #557 for zones to work right but as is it is pretty fantastic. Nice work @rtertiaer