[FEA]: Investigate support of vector types

There certain vector types, that we could / should support better, e.g int2/4/8

We should consider adding support for those within libcu++, especially regarding type traits.

Another example are performance optimization we are employing for built in types, that should also be doable for those vector types, e.g. https://github.com/NVIDIA/libcudacxx/pull/449