Add native duplex support to Pipewire

[SolarLiner]

This can be done by creating a Pipewire filter, which supports arbitrary inputs and outputs, and allows us to work with both input and output buffers at the same time.

[Be-ing]

I looked into this several years ago when I was considering what audio APIs/libraries to use. Unfortunately the Pipewire Rust bindings still do not have safe bindings for pw_filter. There is an old stalled PR with outstanding issues.

There is a project to reimplement the Pipewire client library in Rust, but that's in early development and doesn't support filters yet either.

For my project, I ended up using the JACK bindings directly due to cpal's limitations and the lack of pw_filter bindings. So I am glad you have started this library to overcome cpal's longstanding limitations.