Fixes https://github.com/flutter/flutter/issues/124247

| Native | Flutter before | Flutter after |
| --- | --- | --- |
| <img width="248" alt="Screenshot 2023-04-05 at 9 26 16 AM" src="https://user-images.githubusercontent.com/389558/230177116-154999e8-eef3-441d-9fe9-7063839a6b99.png"> | <img width="240" alt="Screenshot 2023-04-05 at 11 18 01 AM" src="https://user-images.githubusercontent.com/389558/230177125-1680e851-223e-4956-b5b6-1a24e11dc22a.png"> | <img width="226" alt="Screenshot 2023-04-05 at 11 17 36 AM" src="https://user-images.githubusercontent.com/389558/230177123-bde82134-67e1-4ce2-8eec-719eeb779bf4.png"> |

Also, it's now possible for anyone to create disabled buttons like this by setting ContextMenuButtonItem.onPressed to `null`.

* Add spell check suggestions toolbar

* Fix test and move menu

* Cleanup

* Cleanup and fix bug

* More cleanup

* Make height dynamic and use localized delete

* Begin adding tests

* Create var checking for results

* Add tests

* Fix analyze (sorta)

* Add back hideToolbar call for testing

* Add back hidetoolbar in ts and delete one in et

* Remove unecessary calls to hidToolbar

* Fix analyze and docs

* Test fix

* Fix container issue

* Clean up

* Fix analyze

* Move delegate

* Fix typos

* Start addressing review

* Continue addressing review

* Add assert

* Some refactoring

* Add test for button behavior

* Undo test change

* Make spell check results public

* Rearrange test

* Add comment

* Address review

* Finish addressing review

* remove unused imports

* Address nits

* Address review

* Fix formatting

* Refactor findsuggestionspanatcursorindex and textselectiontoolbar constraints

* Fix analyze:

* Can show context menus anywhere in the app, not just on text.
* Unifies all desktop/mobile context menus to go through one class (ContextMenuController).
* All context menus are now just plain widgets that can be fully customized.
* Existing default context menus can be customized and reused.