* dart fix --apply

* manual fixes

* Use `curly_braces_in_flow_control_structures` for `material`

* include test/material

* add back removed comments

* migrates lib/foundation and lib/widgets

* migrates lib/painting and lib/material

* migrates lib/cupertino, lib/gestures, lib/services, lib/semantics and lib/rendering

* fixes failing tests

* migrates test/

* improves hashing of lists

This reverts commit 81439922.

* migrate some material files to nullsafety

* review

* add language version 2.8 in packages/flutter

* enable non-nullable analyzer flag