This reverts commit 53e68762.

* allow marking a golden check as flaky

* add matchesFlutterGolden to analyze.dart; no tags for flutter_goldens/lib

* Pause

* ++

* ++

* Analyzer therapy

* Once more with feeling

* Nits

* Review feedback

* Silly oops

* Test progress

* More tests

* Finish

* Nits

* Analyzer

* Review feedback
Co-authored-by: Yegor Jbanov <yjbanov@google.com>