prefer_contains does not catch type parameters bound to Iterable (or promoted to)

[srawlins]

Describe the issue

prefer_contains does not catch type parameters bound to Iterable (or promoted to a bound of Iterable). For example:

To Reproduce

bool typeVariableBoundToList<T extends List<int>>(T list) =>
    list.indexOf(1) < 0; // LINT

bool typeVariablePromotedToList<T>(T list) =>
    list is List<int> && list.indexOf(1) < 0; // LINT

Expected behavior

Each of these should be reported.

Additional context

The recent typeForInterfaceCheck extension method on DartType should help. only_throw_errors needed a similar fix.