Warn if object detection video mode (width or height) does not match model size

[mcm001]

If we feed a 640x640 model a 640x480 image we only have to pad, not also resize. This can reduce latency and overhead. Show a little warning if this is not the case

[samfreund]

This should be done once #1748 is completed.

[mcm001]

Is that in scope for that MR? This seems distinct to me.

[samfreund]

Is that in scope for that MR? This seems distinct to me.

It is distinct, I just mean that we ought to wait until after #1748 as it's going to change how OD metadata is stored.