There was a case where we could end up having more buffers on the sinkpads
than what was expected, depending on timings. This ensure that we have a fixed
number of buffers produced by the testsrc, and we play until EOS.
Replace theora encoder/decoder chain with fakevideodec for testing
QoS handling in videorate rate property tests. This simplifies the
test pipeline and removes dependency on theora codecs.
Also adjust test expectations to match RGBA format output from
fakevideodec instead of I420 from theoradec, and limit buffer
counts to make tests more deterministic.
This also fixes the rate we set for 2.0 test as we were actually testing
0.5 there.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/9013>
fac2d62054