fix(magnify_ime): Remove typing delay for magnify keyboard

- Immediately delegates all touch events performed over the keyboard
  while not magnified, except for the first tap after triggering
  a magnification shortcut.
- Delegates all finished taps performed over the keyboard while
  magnified.

This has the effect of preventing the user from performing the triple
tap shortcut over the keyboard. The user must triple-tap outside the
keyboard region in order to activate or deactivate magnification.

This may require panning before they can deactivate, if the user has
zoomed the keyboard to take over the entire screen. As a fallback the
user can always lock the screen if they are confused or feel stuck
and magnification will reset the zoom level (existing behavior).

Fix: 413446643
Flag: com.android.server.accessibility.enable_magnification_magnify_nav_bar_and_ime
Test: atest FullScreenMagnificationControllerTest
Test: atest FullScreenMagnificationGestureHandlerTest
Change-Id: I3dafc39980c825731bde048864e6be847c45eadf