Support following typing foucs in window mode [2/n].

There are 3 milestones in this feature.
1. Refactor the callbacks for Accessibility in WindowManagerInternal.
2. Implement this feature in such new architecture.
3. Implement the setting choice in preference page.

This CL is for the 2nd milestone.

We move the window magnification to the typing focus' center position
based on the condition of whether a user takes control or not. We only
make a movement when the control is not taken by a user or we don't
preform the movement for the window magnification.

There are 2 methods for a user to take the control.
1. A user use 1 finger to drag the window magnification.
2. A user use 2 finger to drag the window magnification.

There is 1 method for a user to release the control.
1. When IME is shown, the control would be released.

So, we can decide whether we should make a movement to typing focus
given the condition of who take the control.

Bug: 194668976
Test: atest MagnificationControllerTest
	atest WindowMagnificationTest
	atest WindowMagnificationControllerTest
	atest WindowMagnificationManagerTest
Change-Id: I145f893d412b74c20afe1685449370d1dba99961