feat(#AlwaysOnMagnifier)!: Supports magnification zooming to 100% [1/2]

There are 2 parts in this feature.
1. support fullscreen magnifier zooming to 100%.
2. support window magnifier zooming to 100%.

This CL is for the 1st part.

We change the minimum magnifiable scale to 100% in fullscreen magnifier, and prevent persistedScale from being 100%.

We adjust the flag mMagnificationActivated's usage and add new function isActivated(). Originally, The services check isMagnifying() to identify the fullscreen magnifier is activated. If the magnifier zooms to 100%, the magnifier state would become activated but not magnifying. Accordingly, the services cannot identify whether the magnifier is activated when zooming to 100%. Therefore, instead of isMagnifying(), the services change to check fullscreen magnifier is activated by isActivated().

We support pinching to zoom gesture after tapping on a11y shortcut to activate fullscreen magnifier. Originally, we can use pinching gesture only when we additionally perform one more tap in advance.

Besides, when magnifier is already activated, we support further zoom in temporary by triple tap and hold gesture. Originally, the gesture only changes the state to the viewport dragging mode.

Constrain the scale range in persisted scale getter/setter to >= 2.0 to prevent the presisted scale from being 100%. It results in zooming in with persisted scale would make context no changes.

Bug: 146504199, 242739712
Test: manually
      atest FullScreenMagnificationControllerTest
      atest magnification/FullScreenMagnificationGestureHandlerTest
      atest cts/FullScreenMagnificationGestureHandlerTest
      atest MagnificationControllerTest
      atest AccessibilityManagerServiceTest
      atest AccessibilityMagnificationTest
Change-Id: I3b0b119e9833eddb9a13681e4631b3ff47c6ce1e