Add amsynth to the "high priority" section

[Slackadays]

amsynth is a popular FOSS MIDI softsynth. To the scheduler, it doesn't look like an important task. Because of that, the scheduler currently gives it a nice value of 5. However, that spells trouble for audio applications because a higher priority task can steal CPU time and create pops or breaks in the synth output. Therefore, amsynth (and maybe other similar pro audio programs, too) should be treated as "high priority."

[Slackadays]

Does system76-scheduler even have a mechanism to give certain programs a high priority regardless of focus? That'd be useful for the kinds of things like amsynth that may or may not be in focus but can't afford losing priority. Windows already has this problem with Intel Alder Lake and the closest thing to a solution there is to manually select some option for the program in question. That might actually be a feature worth adding to Pop!_OS.

[mmstick]

Sounds like a bug. The scheduler service should retain priority for things that have a priority manually defined.

[mmstick]

Superseded by #32