Fix hint text updates in Extracted text mode

Updates to the hint on a TextView were not notified to the
ExtractEditText, so there was no way it could know to update.
This change pipes through the hint value when the extracted
mode becomes visible and informs it of changes.

The Editor#reportExtractedText method has been refactored to
be more readable. Note that checks on whether the content
changed are done in the two places in the code that already
called this method, and we explicitely don't want to check
contents when there is a hint change.

Bug: 63980155
Bug: 65691495
Test: bit CtsWidgetTestCases:.TextViewTest
Change-Id: I357dd5c74b61d149cf8612d1f52c7118ec70c696