Blender Git Loki

File/Asset Browser: Select/Activate File on Right Click for Context Menu

Right clicking would spawn the context menu under the cursor, but some
operators would actually act on the active asset/file which wasn't
the one clicked on.

When multiple files are selected and one of them is right-clicked on,
selection is not changed to allow operations on multiple files. E.g.
deletion.

This makes the File/Asset Browser match the Outliner (in behavior, not
implementation).

For the right-click selection keymap:
* The context menu still only spawns on W.
* Bonus: Right click now does something, it actually selects files!
I could have done additional changes here to avoid this, but it seems
like a good addition.

This is also a better alternative to rB5edfde58fe60, which didn't work
properly either. Using rename from the context menu would only work if
the clicked on file was also active...

Differential Revision: https://developer.blender.org/D12065

Reviewed by: Campbell Barton