libs: encoder: vp9: Improve the manner to decide the profile.
libs: encoder: vp9: Improve the manner to decide the profile.

We should decide the VP9 encoder's profile based on the chroma and
depth of the input format, then make sure it is included in the
allowed list.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer-vaapi/-/merge_requests/380>

GStreamer/gstreamer-vaapi,GStreamer/gstreamer-vaapi