Support Validation for Recursive Types in the Verifier

[Y-Nak]

We need to implement validation for recursive types in the Verifier. However, recursion through indirection using pointers should be allowed.

Example (indirection recursion that should be allowed):

type public @Node = { *@Node };

In this example, the recursion occurs via the next pointer, which does not require validation.

Example (direct recursion that shouldn't be allowed):

type public @X = { @Y };
type public @Y = { @X };