• Small fixes for the Gtk4 port found by coderabbitai
• Use create_popover and PopupManager in _create_and_show_keybindings_edit_popover()
• Test Vietnamese m17n marks typed after the syllable in m17n-db 1.8.17 (by nguyenphivn vietphi.dang@gmail.com)
• Adapt Vietnamese m17n tests to modern tone mark placement in m17n-db 1.8.17 (by nguyenphivn vietphi.dang@gmail.com)