a11y atspi: Misc fixes for AT-SPI Text methods GetCharacterExtents, GetRangeExtents and GetOffsetAtPoint
requested to merge michaelweghorn/gtk:michaelweghorn/a11y_atspi_getcharacterextents_getoffsetatpoint_fixes into main
Improve recently introduced AT-SPI Text methods GetCharacterExtents, GetRangeExtents and GetOffsetAtPoint:
- fix incorrect types causing GetOffsetAtPoint to not work
- let GetCharacterExtents and GetRangeExtents report the proper width + height
- support parent-relative coordinates
- make them work for non-GtkWidget GtkAccessible implementations
(See the individual commits for more details.)