Make mirror view able to move close to the screen edges

Because magnification mirror view has transparent border,
the mirror view unable to move close to the screen edges visually.
So we use setTranslationX and setTranslationY to adjust the
location of mirror view to achieve it.

Bug: 146402201
Bug: 148356962
Test: adb shell settings put secure window_magnification 1
Change-Id: I1491ad8113faaa1a559df776f8c6920935dea505