Blender Git Loki

UI: Fix T76918: 3D Mouse Inconsistent / Inaccessible UI

This consolidates the UI code for NDOF input settings, making all
settings accessible from the preferences. This works around an issue
where the Space Navigator's "Menu" button doesn't trigger the settings
menu in Blender.

I also took the opportunity to redo the UI layout.

Note: Separate commit for 2.83 because UI layouts features
have diverged.

Differential Revision: https://developer.blender.org/D7806