PipeWire implementation

[valaphee]

This PR implements PW,

it works by having a main loop and use uni-directional channels to pass control messages to the main loop.

There are some open questions, and I use jack as foundation. For example there is not really any equivalent for devices, maybe it can be set that a device is the node the newly created node connects to.

Or its just like Jack, that there is a default device, and the user can create devices. But each individual stream should be a node.

As I can't test with ALSA, when a stream is dropped it gets released and its a permanent operation in contrary to play and pause which are temporary. Theoretically play and pause could also be mapped to connect, disconnect, but idk if this is correct.

Fixes #554

[valaphee]

Its WIP because of the open question and it needs some polishing, I also temporary didn't mark it as separate feature as otherwise my code completion doesn't work.