* 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.

This reverts commit 51acda81.

* Update Cupertino text input padding

* Remove comment

Fixes scrolling by dragging a selection when the field is in a Scrollable.

This reverts commit ff9fe356.

* added Magnifier for iOS and Android

Fixes a fidelity bug on desktop involving the selection toolbar not hiding when it should have.

* Use `curly_braces_in_flow_control_structures` for `animation`

* Use `curly_braces_in_flow_control_structures` for `cupertino`

* fix comments

* Revert "Add default selection style (#100719)"

This reverts commit c8057bc5.

* update

* update

This reverts commit c54ce015.

Before this change, it was possible to select and copy obscured text from a text field.

This  changes things so that:
- Obscured text fields don't allow copy or cut.
- If a field is both obscured and read-only, then selection is disabled as well (if you can't modify it, and can't copy it, there's no point in selecting it).

SelectableText defers to EditableText for wantKeepAlive, plus improved docs.