pulsesrc: Move to extended stream API

This is needed as a precursor to allowing capture of IEC61937
formats. We now also need to include the channel map while converting
format info to caps so that a correct channel mask is generated for
pulsesrc's caps.
8 jobs for pulsesrc-extended-api in 54 minutes and 29 seconds (queued for 3 minutes and 7 seconds)