Reverts flutter/flutter#131998

Reverting for https://github.com/flutter/flutter/issues/132222

Fixes https://github.com/flutter/flutter/issues/59413

This relocates `mock_canvas.dart` and `recording_canvas.dart` from `flutter/test/rendering` to `flutter_test`. 

The testing functionality afforded by mock_canvas should be available to everyone, not just the framework. :)

mock_canvas.dart needed a bit of cleanup - things like formatting and super parameters.

It's time to say good bye to an old friend. 
It has outlived its usefulness.
Farewell, AbstractNode! 🫡

Updates most of the unit tests in the packages/flutter/test/material folder so that they'll pass if ThemeData.useMaterial3 defaults to true.

All of the tests have wired useMaterial3 to false and will need to be updated with a M3 version.

related to #127064

This reverts commit d2788080.

* Check whether slider is mounted before interaction, no-op if unmounted (#113556)

* Check whether slider is unmounted before interaction

* Update slider.dart

* Update Slider

* Add test

* Update slider_test.dart

* Update packages/flutter/test/material/slider_test.dart
Co-authored-by: Taha Tesser <tessertaha@gmail.com>
Co-authored-by: Taha Tesser <tessertaha@gmail.com>

* exposed tooltip longPress action when available

* updated tooltip test

* updated date picker test

---------
Co-authored-by: Mingyu <lyming90@gmail.com>
Co-authored-by: Taha Tesser <tessertaha@gmail.com>
Co-authored-by: Harper Liu <harperl0818@gmail.com>

* Revert "Exposed tooltip longPress action when available (#117338)"

This reverts commit 38e3930f.

* Revert "fixes android_semantics_integration_test to expect long press for tootip"

* Enable  lint

* note about discarded_futures

* note about use_decorated_box

* update note on require_trailing_commas

* Exposed tooltip longPress action when available (Trigger mode is long press)

* Use `curly_braces_in_flow_control_structures` for `material`

* include test/material

* add back removed comments

This reverts commit 35ad43f2.

This reverts commit c26ed03c.

* Migrate to ChannelBuffers.push

* Move TestDefaultBinaryMessenger to its own file

* Apply deprecations and fix usages

* Add semantics sort key for modal scope and modal barrier

* fix test

* fix test

* fix test

* fix space

* fix more tests

* addressing comments

* add language version 2.8 in packages/flutter

* enable non-nullable analyzer flag