Linter: False positive unrelated_type_equality_checks for certain generics cases

[camsteffen]

I found a false positive for unrelated_type_equality_checks similar to #1297 but more specific.

class Foo<T> {
  Bar<T> bar;

  bool test(Baz baz) => bar == baz; // false positive here
}

class Bar<T> {}

class Baz extends Bar<int> {}

[pq]

fyi @srawlins who's fixed a bunch of issues in this one recently.

[srawlins]

Hey now, I never said I _enjoyed_ working on unrelated_type_equality_checks. 😛