Blender Git Loki

Asset Browser: Adjust header pulldowns to be Asset Browser specific

So far the Asset Browser just showed the same menus as the File Browser.
Not all of their entries made sense for the Asset Browser though. I
decided to just give them entirely different classes to avoid confusing
if-else checks everywhere. I think the code duplication this adds is a
minor issue, it's better to keep things seperated clearly IMO.

* View menu: Add "Asset Details" toggle for the sidebar region.
* View menu: Remove recursion sub-menu
* View menu: Remove "File Path" region toggle, which doesn't apply for
the Asset Browser.

Differential Revision: https://developer.blender.org/D12057