Adding flame_lint and removing dart code metrics (#1049)

* Adding flame_lint and removing dart code metrics

* Update packages/flame_flare/example/pubspec.yaml

* updating analyze action

* adding missing dardoc dep on flame_lint

* removing test folder from the lint package

* fixing sdk versions

* license and changeog fix

* Update packages/flame_lint/README.md

Co-authored-by: Lukas Klingsbo <lukas.klingsbo@gmail.com>

* additional readme fix

Co-authored-by: Lukas Klingsbo <lukas.klingsbo@gmail.com>