bluetooth: adjust sync to source with different sample spec
requested to merge igor.v.kovalenko/pulseaudio:pr/bluetooth-sync-with-different-sample-spec into master
If source and sink sample specifications are different, calculate write budget increment via size of received frame in microseconds.
All current profiles have equal source and sink sample specifications, so this change is not immediately useful but is needed when source/sink will e.g. have different sample rate.