Add a test for flexfec with bandwidth variation to see how the level of the parity protection adapts, for a given loss rate.
Add a test to compare the received framerate measurement in the video stream with and without flexfec. The number of anomalies are compared (an anomaly occurs when the video output is blocked). The number of anomalies should be smaller with FEC. The test is run several times in case of fail (max 3) because of its non deterministic behaviour.

Update other tests with FEC: get the bandwidth used for the FEC for tests.
Disable all video codecs except AV1 for all tests, except the bandwidth variation test that uses VP8.

Add the bandwidth of the FEC in logs of the RTP session.
Add a function to test if the FEC is enabled.

Tester: add functions wait_for_until_for_uint64 and wait_for_list_for_uint64 to use uint64_t statistics.

Fix memory leak in test "Call with file player".

Cmake : move cpp files from SOURCE_FILES_C to SOURCE_FILES_CXX in cmake fil...