fix(#Magnification): magnification gesture handler might not be activated after config transition

If the magnification mode transition is triggered by magnification config, the AccessibilityManagerService would not be notified. It might cause some issues.
1. The AccessibilityUserState would stay in old/wrong mode not same as current mode
2. the AccessibilityInputFilter would not be notified, and thus it would not switch to the corresponding magnification gesture handler

Therefore, in MagnificationController#transitionMagnificationConfigMode, we adjust to notify the service the mode changed, and the service would notify the userState and inputFilter as its original behavior.

Bug: 278031878
Test: manually
      atest MagnificationControllerTest
Change-Id: I7d567873b35eefd7a5a515cb7692d48413a7dd9d