[Magnifier - 10] Make it public

* moves the Magnifier from com.android.internal.widget to
  android.widget
* removes useless public getters; useless for now because we have
  no magnifier configuration but the hardcoded one

Bug: 67839742
Bug: 63531115
Test: bit CtsWidgetTestCases:android.widget.cts.MagnifierTest
Change-Id: Ie6f474c4c781038650007a15937d61c650ee5fdd
3 files changed