adjust migrateAccessibilityButtonSettings to check every shortcut type

some shortcuts were being unnecessarily migrated because we weren't checking the settings for every type.

I took the opportunity to also refactor A11yUserState to enable fetching multiple shortcut types at once.

Bug: 374373185
Test: atest AccessibilityManagerServiceTest AccessibilityUserStateTest, and manually verify the conditions in the bug no longer occur
Flag: android.provider.a11y_standalone_gesture_enabled
Change-Id: Ib9f62a20a88d09e3e2c1ecc3fec49d052d98b448