New keyguard user switcher

 - Use ViewController for KeyguardUserSwitcher, name this
   KeyguardUserSwitcherController

 - Create KeyguardUserSwitcherListView. Separate view container and
   controller code.

 - Daggerize KeyguardUserSwitcherController

 - Move KeyguardUserSwitcher from NotificationsQuickSettingsContainer to
   NotificationPanelView

 - Hide clock and notification when keyguard user switcher is open

 - Show "End guest session" button when switcher is open and user is
   guest

 - Introduce listener for user switcher state

 - Change icon of guest when current so that it does not show exit icon

 - Disallow guest exit via user switcher list item

 - Propagate dark amount to keyguard user switcher

 - Updated styles

Known issues:

 - If repeatedly pressing KEYCODE_POWER while switching between users,
   the clock will sometimes get stuck in INVISIBLE state: b/179930842

 - Multiple StrictMode violations are still present: b/179913579

Test: atest com.android.keyguard
Test: Build with config_keyguardUserSwitcher=false, enable multi-user,
      check that user icon is in the status bar but not on the keyguard
      above the clock
Test: Build with config_keyguardUserSwitcher=true, check that user icon
      is visible on keyguard above the clock
Test: When config_keyguardUserSwitcher=true, tap user icon to open
      keyguard user switcher, then open and close QS to verify that
      the keyguard user switcher closes
Test: Check that user switcher is always open and visible on the lock
      screen when simple user switcher is enabled:
        adb shell settings put global lockscreenSimpleUserSwitcher 1 &&
          adb shell stop &&
          adb shell start

Bug: 169783558
Change-Id: Iaea4eae358873ae80748ca3eb9329f22bb2bb2ef