First of we get rid of the bindings between from "lport-rtp" and "lport-rtcp" to
the "port" property of the udpsrc elements. The properties themselves will get
removed a little later as the required changes are rather intrusive and we need
some more infrastructure in place before we can do the switch.
This is the first step in getting rid of the requirement to have the codec set
during object construction. The goal is to have pipelines prepared in advance so
that the codec can be plugged in once negotiation is complete.
Having the pipelines prepared in advance let's us grab allocated local ports of
udpsrc elements for RTP and RTCP instead of setting those and hoping they're not
yet in use.
This is useful for tests where "pulsesrc" and "pulsesink" GstElements may not
be available (for example in CI).
Additionally only set the echo cancellation and buffer properties for the
pulse GstElements.
Shuffle the code around and make use of docstrings to conform to
the newly introduced coding style as described in `HACKING.md`
This commit also introduces docstrings describing each source file.
These messages are mainly useful for development. This part will be rewritten
once we introduce structured logging. For the moment this will just add noise.
