[Magnifier - 4] Batch of tweaks

* magnifier zoom from 1.5 to 1.25
* max scale from 10 to 4
* magnifier shows over the text if there is no more space above
  instead of showing underneath the cursor
* paused the blink while showing the magnifier and resumed when
  dismissing

Bug: 63531115
Test: bit FrameworksCoreTests:android.widget.TextViewActivityTest
Test: bit CtsWidgetTestCases:android.widget.cts.TextViewTest
Test: manual test that shows the magnifier working
Change-Id: Ief3e0b7dc9e287e7dd1a9102548b1861598b69c4