[A11y] Add DATA_TEXT_CHARACTER_LOCATION_IN_WINDOW_KEY to AccessibilityNodeInfo

Updates TextViews to populate this extra using window coordinates
instead of screen coordinates.

Design doc: go/androidExtraDataTextCharacterInWindow

Bug: b/375429616
Flag: android.view.accessibility.a11y_character_in_window_api
Test: CQ + new tests
Change-Id: I6a35df900b117c658ebd577a64acafe3f96f4abd