Lint that flags uses of Map, Set, or List with keys outside the domain of the type

[Hixie]

According to #48030, it's intentional that you can do things like:

  Map<String, int> foo = {};
  // ...
  print(foo[2]); // prints null, since foo cannot possibly contain an entry with key 2

It would be nice if that tripped a lint to warn you that you're doing something almost certainly invalid.

This would apply to all the methods and operators on the container classes that are defined to take Object? instead of K.

[parlough]

Related: #57844 and #58427

[srawlins]

Duplicate of #58427 and #57434 and #57844