Dynamically load libpulse.so.0 and libasound.so.1 on Linux

By generating stubs using https://github.com/hpvb/dynload-wrapper we
can dynamically load libpulse and libasound on systems where it is available.
Both are still a build-time requirement but no longer a run-time dependency.

For maintenance purposes the wrappers should not need to be re-generated
unless we want to bump pulse or asound to an incompatible version. It is
unlikely we will want to do this any time soon.

This closes #20978

drivers/pulseaudio/audio_driver_pulseaudio.cpp

@@ -233,6 +233,10 @@ Error AudioDriverPulseAudio::init_device() {
 }
 
 Error AudioDriverPulseAudio::init() {
+	if (initialize_pulse()) {
+		return ERR_CANT_OPEN;
+	}
+
 	active = false;
 	thread_exited = false;
 	exit_thread = false;