Blender Git Loki

Asset Browser: Reduce paddings & margins between previews

The paddings and margins were more than needed, this reduces them a bit. That
way space is used more efficiently, the small differences add up so that more
items fit into a row.
The File Browser should not be affected.

Before/after comparisons:
{F11529986} {F11529988}
{F11529987} {F11529989}