Improve Slimproto integration (#701)

Improve Slimproto integration (#701)

* Restore previous power and volume levels for slimproto players

* fix race condition for reconnections

* bump aioslimproto

* make output codec configurable for all player types

* add pcm

* enforce pcm for airplay

* disallow disabling of provider if it has dependents

* typo

* add some missing button commands

* merge lms cli with slimproto

* bump aioslimproto

* base implementation for cometd cli

* implement cometd

* some optimizations

* improve discovery logic

move to aioslimproto later when tested

* bump aioslimproto

* lint