fix: Prevent buffers from being wasted on a paused wayland recorder

[4JX]

As it currently stands, a paused WaylandVideoRecorder will use up its allocated "buffers" by returning from process() without queuing the buffers back. This makes it stop issuing calls to process entirely which makes the thread get stuck and unable to resume with a later call to start().

In pipewire-rs this is handled automatically when calling dequeue_buffer() since the returned Buffer automatically handles this in its Drop implementation.

I assumed that the intended behaviour of start/stop is to pause/resume rather than fully disassemble and reassemble the recording stack on each call.

Refs:

• https://docs.pipewire.org/page_streams.html#ssec_consume
• https://docs.pipewire.org/group__pw__stream.html
• https://gitlab.freedesktop.org/pipewire/pipewire-rs/-/blob/main/pipewire/src/buffer.rs#L46-52