Add adaptive Checkbox and CheckboxListTile

* Fix typos

* lowercase animated & opacity

* Undo typo fix

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Co-authored-by: Michael Goderbauer <goderbauer@google.com>

* remove newline

* update crswap

* add const constructor

* update const

* update m3 values

* update test formatting

* update crswap

* update test

* update token value

* update tests

* Add error state support for side property

* lint fixes

* lint fixes

* remove down position from toggleable ripple

* Introduce tests for tristate checkboxes

* Initial

* Use tristate changes in engine

* Flutter_test matchers test update

* Comments, tests

* Update packages/flutter/lib/src/semantics/semantics.dart
Co-authored-by: Chris Bracken <chris@bracken.jp>

* Assert mutual exclusivity

* Assert valid state before updating state

* Update packages/flutter/lib/src/semantics/semantics.dart

Typo fix in comment
Co-authored-by: Loïc Sharma <737941+loic-sharma@users.noreply.github.com>
Co-authored-by: Chris Bracken <chris@bracken.jp>
Co-authored-by: Loïc Sharma <737941+loic-sharma@users.noreply.github.com>

This reverts commit 5fd259be.

This reverts commit d056500b.

This reverts commit 31de052e.

This reverts commit e2490f29.

This reverts commit 35ad43f2.

This reverts commit c26ed03c.

* Migrate to ChannelBuffers.push

* Move TestDefaultBinaryMessenger to its own file

* Apply deprecations and fix usages