Clean up CarUserManagerHelper methods only used in Settings [1]

Started cleaning up methods only used in the Settings app.
  - #isForegroundUserGuest
  - #hasUserRestriction
  - #canCurrentProcessAddUsers
  - #canCurrentProcessRemoveUsers
  - #scaleUserIcon
  - #setUserRestriction

Also added 2 tests to DevelopmentSettingsUtilTest around DISALLOW_DEBUGGING_FEATURES flag.

To update tests, I needed to introduce more usage of ShadowUserManager.
There's a bug with the implementation around UserRestrictions, so I had
to add a redirect method for setUserRestriction() to our subclass ShadowUserManager.

Bug: 137136907
Test: atest CarSettingsRoboTests
Test: atest CarUserManagerHelperTest
Change-Id: Ica186ce84d604db9ee20a0dd4ccc430e60d65e11
18 files changed
tree: ad2d5ccec323017f883e3cc9a455a832bd3ae4dc
  1. res/
  2. src/
  3. tests/
  4. Android.bp
  5. AndroidManifest.xml
  6. PREUPLOAD.cfg