[mlir][VectorToGPU] Fix support for i4, col-major operand support

For the conversion to nvgpu `mma.sync` and `ldmatrix` pathways, the code
was missing support for the `i4` data type. While fixing this, another
bug was discoverd that caused the number of ldmatrix tiles calculated for
certain operand types and configurations to be incorrect. This change
fixes both issues and adds additional tests.

Differential Revision: https://reviews.llvm.org/D128074