fix(js): comments after superclass (#8312)
* Fix comments after superclass
* add changelog
* refactor
* Organize tests
* Use addBlockStatementFirstComment
* Amend unstableTests list
* Avoid identical comments in tests
* Add tests for `implements`
* Handle comments in interfaces
* Remove an always-false condition
* Almost a fix
* Further fixes
* Add DeclareClass
* Add DeclareInterface, mixins
* Fix extends in DeclareClass
* Fix DeclareClass
* Fix mixins
* Refactor: remove unused parameters
* Add marked dangling comments
* Unify printing of interface for TS and Flow
* Fix unstable interfaces
* Remove comment
* Restore the original behavior for interfaces with multiple inheritance
* Refactoring, tests
* Remove unused code
* Include a file accidentally omitted from the merge commit
* Remove unused type import
