[Magnifier-69] Some cleanup in API names and docs

This CL:
- renames setForcePositionWithinWindowSystemInsetsBounds to
setClippingEnabled
- improves some of the docs

Bug: 120609112
Test: atest CtsWidgetTestCases:android.widget.cts.MagnifierTest
Change-Id: I14c774b432b4a0cff96066734758b9f937179d94
2 files changed