Fix projected covariance interfaces

[manodasanW]

• In the AOT optimizer, for collection types with value types as the generic instantiation, we were projecting a covariant interface on the vtable for IEnumerable when it isn't a covariant interface. This addresses that by fixing the check for it.
• Added tests to validate scenarios where the interface should be projected and shouldn't.
• During testing, it was discovered for collections of interfaces, we were not projecting object as a covariance given BaseType returns null for interfaces. This is addressed by an interface check that was added.