* Use `curly_braces_in_flow_control_structures` for `widgets`

* fix comments

* fix comments

* Support global selection

* addressing comments

* add new test

* Addressing review comments

* update

* addressing comments

* addressing comments

* Addressing comments

* fix build

* fix deprecated_new_in_comment_reference for `material` library

in a future version of the SDK, these will be flagged, fix them now

* Update pubspec.yaml

Co-authored-by: Zachary Anderson <zanderso@users.noreply.github.com>

This reverts commit d056500b.

This reverts commit 31de052e.

This reverts commit e2490f29.

Fix flutter in preparation for implementing Dart's "Infer non-nullability from local boolean variables" (#72494)

When https://github.com/dart-lang/language/issues/1274 (Infer
non-nullability from local boolean variables) is implemented, flow
analysis will detect that code like this no longer needs to perform a
null check:

    final bool contextIsValid = focus != null && focus.context != null;
    ...
    if (contextIsValid) {
      ... focus! ... // Null check unnecessary
    }

To avoid a build failure due to the unnecessary null check, we need to
temporarily write it in a way that we can ignore it.  Once the feature
is complete and rolled into flutter, I'll remove the null check
entirely.

This reverts commit 9b56241e.

This reverts commit 1f0df545.