add PipeWire audio driver

[mmitch]

I've already got a working prototype, it will need to be cleaned up a bit and get reviewed.

• [x] brush up and rebase experimental commits
• [x] fix stuttering after resuming from pause
• [x] lower plugin priority, don't automatically choose to run it (it's too experimental for that)
• [x] decide for/against using pkg-config in configure
• [x] add to CI pipeline
• [x] update translations
• [x] add to HISTORY and manpages
• [x] update copyrights