Differentiate between type parameters and wildcards

[Gabriel-Darbord]

Currently there is a single entity to represent all type parameters, including wildcards: FASTJavaTypeParameterExpression.
However, there are 2 issues with mixing both of them:

• wildcards are only applicable on variables (not classes and methods, unlike type parameters)
• wildcards have the additional capacity to be bounded by an upper or a lower bound, which is currently not possible to represent

class MyClass<T> {} // OK
class MyClass<?> {} // NOK

<T> void f() {} // OK
<?> void f() {} // NOK

List<T> list; // OK
List<?> list; // OK

// bounded wildcards
List<? extends MyClass> list; // upper bound
List<? super MyClass> list; // lower bound