We missed the case for `ForAll` types (for generic methods)

Fixes #1129

Fixes #1151 

The extra check in `CheckIdenticalNullabilityVisitor` is not needed to
fix this bug but seemed like a prudent addition.

…lUnmarked` method (#1163)

Fixes #1162

This PR infers nullability of generic method type arguments for the case
where the result of the call is assigned to a variable, e.g.:
```java
  class Foo<T extends @nullable Object> {
    Foo(T t) {}
    static <U extends @nullable Object> Foo<U> make(U u) { return new Foo<>(u); }
    void test() {
      Foo<@nullable Object> f1 = Foo.make(null); // legal
      Foo<Object> f2 = Foo.make(null); // error reported; arg cannot be @nullable
    }
  }
```
See the tests for (many) more examples.

---------

Co-authored-by: Manu Sridharan <[email protected]>

Fixes #1156

When checking correctness of lambda overrides we get the type from
`javac`'s inferred type rather than using the enclosing class. Also,
when getting the type of an anonymous class we add some extra assertions
to ensure we find the right `NewClassTree` representing the anonymous
class. I _think_ we'll always get the right tree now, but the asserts
give peace of mind.

Fixes #1160 

Add more tests for other cases also

We suppress some warnings on tests as they will be much easier to fix
with text blocks, which we can only use once we require JDK 17 (see
#1170).

)

Fixes #1173 

In JSpecify mode, we should rely on our checking of generic types and
not treat `@ParametricNullness` as a `@Nullable` annotation.