Blender Git Loki

File Browser: scroll selected files into view

Add operator `FILE_OT_view_selected` to the file browser (and thus also
to the asset browser) that scrolls selected files into view.

This includes the active file, even though it is not selected. In
certain cases the active file can loose its selected state (clicking
next to it, or refreshing the asset browser), but then it's still shown
in the right-hand sidebar. Because of this, I found it important to take
it into account when scrolling.

This also includes a change to the keymaps:
- Blender default: {key NUMPAD_PERIOD} is removed from the "reload"
operator, and assigned to the new "view selected files" operator. The
reload operator was already doubly bound, and now {key R} is the only
remaining hotkey for it.
- Industry compatible: {key F} is assigned to the new "view selected
files" operator. This is consistent with the other "view selected"
operators in other editors.

Reviewed By: Severin

Differential Revision: https://developer.blender.org/D10583