Blender Git Loki

UI: Expand tree-view items (e.g. asset catalogs) on click to activate

This actually gives a quite nice behavior in my opinion, especially for
asset catalogs, where activating a catalog makes all assets inside it or
its (grand-)child catalogs visible, so showing the child catalogs then
adds useful information. Maybe this should become a feature for
asset catalogs only, to be evaluated once the tree-view API is used in
more cases. Only asset catalogs are affected by this change right now.

Part of T93582.