feat(magnify_ime): Add Option to Magnify Navigation Bar and IME [2/2]

Users who use screen magnifier now have the option to magnify
their navigation bar and IME (e.g. keyboard). We implement this through
a new Secure Setting monitored through the AccessibilityManagerService,
which can be toggled by a user in the Settings.

NO_IFTTT=already sync it

Bug: 342509709
Flag: com.android.server.accessibility.enable_magnification_magnify_nav_bar_and_ime
Test: manually
Test: atest MagnifyNavAndImePreferenceControllerTest
Test: atest ToggleScreenMagnificationPreferenceFragmentTest
Change-Id: I880da997a7f23b746bc0ef3b4b5f072b7648d311