Optimize magnifier viewport drawing

1. Reduce the number of drawIfNeeded calls in fullscreen mode by 99%.
Because updateMagnificationSpec -> setMagnifiedRegionBorderShown will
be called with motion events when changing zoom. Then even if the
border region is not changed, it still always forces redraw. So simply
skip if the border shown state is not changed.

2. Only apply surface transaction if related attributes are changed.

3. drawIfNeeded was always called inside WM lock, so the change [1]
didn't work. With this change, drawIfNeeded is still called on the
same animation thread but it is executed from message directly,
then the change [1] can take effect that avoids holding WM lock
when calling lockCanvas.

[1]: Id828744c8c5bcb4bdb3be9a11810338614b84b2e

Bug: 276845499
Fix: 316075123
Test: atest AccessibilityMagnificationTest
Change-Id: Ibbb9f86112bf734cd0d2cd27f39aabcd13e003cc