Rather than always snapping the region size to the closest multiple of
the row height, remember the amount of rows displayed after the user
resized the region, and try to preserve that. This gives a lot more
predictable behavior, especially when the "Show Names" option is toggled
on and off, and the region resizes in response. With the old method the
amount of visible rows could change multiple times while toggling.
This also enables us to clamp the amount of rows (e.g. while the preview
size is increased and the region becomes too large for the area; or,
when a catalog tab is activated with fewer assets and thus fewer rows)
but still restore the amount of rows the user chose earlier, as soon as
possible.
Part of #107881.
Pull Request: https://projects.blender.org/blender/blender/pulls/112637
998e8d0ef6