fix(MultiFingerMultiTap): Delete lots of duplicated code

Narrow the scope of the flags, making them as specific as possible to indicate the exact areas they affect. Avoid duplicating entire classes, so that the logical differences between the flag being on and off are immediately apparent.

Bug: 356322729
Test: atest -c FullScreenMagnificationGestureHandlerTest
Flag: com.android.server.accessibility.enable_magnification_multiple_finger_multiple_tap_gesture
Change-Id: I9d65bee086eb9ad96d5851a851f8d0853cd766b4