Fix recursive pointerof detection with generic splat type variables

[HertzDevil]

Fixes #11808. This happens with any generic class type that has a splat type parameter, not just Tuple.

class Foo(*T); end

x = Foo(Int32).new
x = pointerof(x) # Error: recursive pointerof expansion: Pointer(Foo(Int32)), Pointer(Foo(Int32) | Pointer(Foo(Int32))), ...

x = 1
x = {pointerof(x)} # Error: recursive pointerof expansion: Pointer(Int32), Pointer(Int32 | Tuple(Pointer(Int32))), ...

class Foo(*T); end

x = 1
y = pointerof(x)
x = Foo(String).new # okay