Test pitch with different forward and backward playback rates. Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/6247>
Needed for https://gitlab.freedesktop.org/gstreamer/cerbero/-/merge_requests/930 Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/3064>
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/2178>