timecodestamper: Fix up handling/queueing of LTC timecodes

timecodestamper: Fix up handling/queueing of LTC timecodes

Directly read them out of the decoder as soon as we passed audio and
then store them in a queue that we handle internally together with their
timestamps. This cleans up memory management and gives us proper control
over the queue instead of guessing how the queue inside the LTC decoder
actually works and when it overflows.