Ensure we get the right nav bar mode for the current user in sysui

- Load resources from the current user's context to ensure the right
  overlays are read
- Create a controller in sysui to dispatch mode change to prevent callers
  from calling with the wrong user's context
- Clean up the quickstep contract to prevent launcher from calling methods
  using the baked in fw resource ids

Bug: 130185871
Test: Switch to secondary user, ensure the mode is read correctly
Change-Id: I00d9276185777e340b3e758345a00d2e9b3e3e64