Use the builder directly to leave the samplerate undefined so that we adapt to the graph samplerate instead of forcing resampling.
source and sink need not be set and need to be mapped to the target source/sink to connect to. node.group needs to be a unique id shared by source/sink to make them part of the same scheduling group and do clock sync. Remove some unused properties
Implements all modargs other than rate adjustment and max latency related ones, which do not make sense in our context. Fixes: https://gitlab.freedesktop.org/pipewire/pipewire/-/issues/543
