Introduce gst_vaapi_surface_proxy_new_from_pool() to allocate a new surface
proxy from the context surface pool. This change also makes sure to retain
the parent surface pool in the proxy.
Besides, it was also totally useless to attach/detach parent context to
VA surface each time we acquire/release it. Since the whole context owns
all associated VA surfaces, we can mark this as such only once and for all.
Make GstVaapiSurfaceProxy only a thin wrapper around a VA context and a
VA surface. i.e. drop any other attribute like timestamp, duration,
interlaced or top-field-first.
GstVaapiSurfaceProxy does not use any particular functionality from
GObject. Actually, it only needs a basic object type with reference
counting.
This is an API and ABI change.
Add new "interlaced" attribute to GstVaapiSurfaceProxy. Use this in
vaapipostproc so that to handles cases where bitstream is interlaced
but almost only frame pictures are generated. In this case, we should
not be alternating between top/bottom fields.
