Make Layout#getRangeForRect public

To avoid making WordIterator public, WordSegmentFinder has a public
constructor taking a Locale parameter. The constructor taking a
WordIterator parameter is kept but hidden so TextView can use it.

LayoutGetRangeForRectTest is moved to CTS.

Bug: 243969224
Test: atest android.text.cts.LayoutGetRangeForRectTest
Test: atest android.widget.cts.TextViewHandwritingGestureTest
Change-Id: Ibb829af0324c47e4d275b0ccd69d0f95601e3c08