si-audio-adapter: parse the rate optionally
We can use spa_format_audio_raw_parse() because we need to parse the samplerate here optionally. Many virtual sinks will not set a rate, which makes parsing fail and the node will end up with the default channels/positions, which is most likely wrong. Fixes channel positions for virtual sinks.
parse-rate-optional in 1 minute and 47 seconds6 jobs for