Don't notify scale change to input when the scale is not changing

This fixes lagging gesture issue when a mouse cursor is visible.

We assume that when we notify a scale change to input, if the scale is
actually not changing, input side can ignore unchanging scale. Thus,
we notified input the scale change unless it's explicitly scale
transient change.

However, during a gesture on touchscreen, changes that may modifies the
scale and changes that don't are mixed. As a result, the latter
actually invokes notifying the input, tries to update the mouse cursor
scale frequently, resulting in a laggy behavior.

To fix this, this change sets "isScaleTransient" to true on
non-scale-moidfying changes.

Bug: 428560746
Test: FullScreenMagnificationControllerTest
Flag: EXEMPT bug fix
Change-Id: Ie36a164ff4f94baedf26cbafacb55c66a5a527dc