* Refactor TextSelectionOverlay

* fix test

* remove print

* fix more tests

* update

* added tests

* fix comments

* fmt

* fix test

* addressing comment

* remove dispose

* remove new line

* Unify Text selection API

* fix test

* further simplify

* fix more tests

* styling change

Supports the desktop text editing interaction of holding shift, tapping the field, and dragging to modify the selection.

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).

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

This PR 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).

This reverts commit 5fd259be.

This reverts commit 43e31977

Simplifying and refactoring parts of RenderEditable. Functionality is the same.

Use the hasStrings clipboard method when possible instead of reading the contents of the clipboard.

Revert "[EditableText] call `onSelectionChanged` only when there're actual selection/cause changes (#87971)" (#88183)