xvimagesink: Handle cropping when copying frames.

xvimagesink: Handle cropping when copying frames.

Cropping was not handled properly when frames have to be copied to
xvimage's buffer pool, first because the crop meta were dropped, and
second because the allocated frame size in xvimage's buffer pool were
smaller than the incoming frame.

This patch updates xvimagesink's video info when propose_allocation()
is called, and copies the GstVideoCropMeta from source frame to
destination one.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/merge_requests/1088>