vaapidecode: use caps to check the features

vaapidecode: use caps to check the features

Instead of calling gst_vaapi_find_preferred_caps_feature(), which is
expensive, we check the caps from the allocation query, to check the
negotiated feature.

In order to do this verification a new utility function has been implemented:
gst_vaapi_caps_feature_contains().

As this new function shared its logic with gst_caps_has_vaapi_surface(), both
have been refactorized.

Signed-off-by: Víctor Manuel Jáquez Leal <victorx.jaquez@intel.com>
https://bugzilla.gnome.org/show_bug.cgi?id=756686