vaapivideobufferpool: rename video info structures
vaapivideobufferpool: rename video info structures

Renamed private GstVideoInfo structure video_info to allocation_vinfo
and alloc_info to negotiated_vinfo.

The purpose of these renaming is to clarify the origin and purpose of
these private variables:

video_info (now allocation_vinfo) comes from the bufferpool
configuration. It describes the physical video resolution to be
allocated by the allocator, which may be different from the
negotiated one.

alloc_info (now vmeta_vinfo) comes from the negotiated caps in
the pipeline. It represents how the frame is going to be mapped
using the video meta.

In Intel's VA-API backend, the allocation_vinfo resolution is
bigger than the negotiated_info.

https://bugzilla.gnome.org/show_bug.cgi?id=783599

ceyusa/gstreamer-vaapi,GStreamer/gstreamer-vaapi,GStreamer/gstreamer-vaapi,ceyusa/gstreamer-vaapi