* refactor out FormattingToolbar and TextEditingDeltaHistoryView from main`
* replace togglebuttonstatemanager and texteditingdeltahistorymanager with appstatemanager
* fix up tests
* clean up
* Add ReplacementTextEditingController to AppState
* formatting
* `dart format`
Co-authored-by: Renzo Olivares <roliv@google.com>
Co-authored-by: Brett Morgan <brettmorgan@google.com>
