libs: window: implements gst_vaapi_window_set_render_rectangle

libs: window: implements gst_vaapi_window_set_render_rectangle

Implements new vmethod gst_vaapi_window_set_render_rectangle,
which is doing set the information of the rendered rectangle set by
user.
This is necessary on wayland at least to get exact information of
external surface.

And vaapisink calls this when gst_video_overlay_set_render_rectangle is
called.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer-vaapi/-/merge_requests/342>