filters: add an operations structure to set the callbacks

Generate a simple operations structure for filters generating their own filter
callback via VIDEO_FILTER_WRAPPER().

The filter chain sets a mouse handler on video filters that don't have one,
just as before, by using a local version of the ops structure of the filter and
adding the local mouse callback.

Co-authored-by: Steve Lhomme <robux4@ycbcr.xyz>