v4l2videoenc: Implement default profile/level selection
Recently there was more and more report of:
v4l2videoenc gstv4l2videoenc.c:440:negotiate_profile_and_level:<v4l2h264enc0> Failed to set H264 profile: 'Invalid argument'
This was reported on downstream driver, notably RPi rpivid and IMX8 malone drivers. These downstream driver do take care of adjusting the profile/level to a valid value and just fail (which is btw against the V4L2 spec). Though, GStreamer is not doing anything either, so perhaps we could implement some logic to select a profile/level pair that is valid for the caps and the input pixel format.