codecs: h264dec: Improve the policy to infer max_num_reorder_frames.

codecs: h264dec: Improve the policy to infer max_num_reorder_frames.

The max_num_reorder_frames number can change the way we bumping the
pictures in the DPB. The smaller it is, the lower latency we will
get. So it is important for live mode streams, but it is not given
in VUI parameters sometimes. We now improve the policy to infer it:
1. Never guess it in the "strict" compliance.
2. For baseline and constrained baseline profiles, which do not have
   B frames, set it to 0.
3. For -intra only profiles, set it to 0.
4. Otherwise, not guess it.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/2501>