Support for non DSP mode

This MR adds support for non DSP mode.

The si-audio-adapter session item has now a disable.dsp configuration property that can be set to TRUE if we don't want to configure the adapter in DSP mode. When doing this, the adapter will be configured in passthrough mode instead, and then, if 2 adapters want to be linked with different formats, the si-standard-link session item will automatically reconfigure one of the adapters in convert mode so that the format matches.

Since the disable.dsp configuration property is per adapter, it is possible to have some adapters configured in DSP mode and others configured in non DSP mode. If a DSP adapter wants to be linked with a non DSP adapter, the configuration of the adapter that is a device node will take preference over the non device adapter.

By default, disable.dsp is set to FALSE so that the default behavior is the same as master.

Finally, keep in mind that monitor ports are not yet supported in non DSP mode. This is because the PipeWire fmtconvert and alsa-pcm-sink plugins don't have a monitor port (only the merger plugin has monitor ports), so in non DSP mode, the monitor nodes won't be able to link. I am looking forward to adding support for monitor ports in PipeWire's audioadapter plugin if configured in non DSP mode at some point in the future.