Fix Image's logical flow which disposes its image too early, causing errors such as "Cannot clone a disposed image" (#110131)

* Add covariant to `ThemeExtension.lerp`

* x

* x

This reverts commit 79013b2b.

This reverts commit 7e33cd5e.

Documentation for Checkbox.value previously did not cover the tristate case.

This reverts commit b3aba4d9 because it breaks Google tests.

* Revert "Revert "Set `IconButton.visualDensity` default to `VisualDensity.standard` (#109349)" (#109421)"
Co-authored-by: Qun Cheng <quncheng@google.com>

* Introduce stubbed `exclusive` parameter to `File.create`-overridden method.

This is to soften landing of a breaking change https://github.com/dart-lang/sdk/issues/49647

* added dropdown and scaffoldmessenger FWW links

* added StatefulBuilder wotw link

* added Autocomplete FWW link

* removed accidental auto-formatting

This reverts commit ff9fe356.