[mlir][NVGPUToNVVM] Add option for emitting opaque pointers

Part of https://discourse.llvm.org/t/rfc-switching-the-llvm-dialect-and-dialect-lowerings-to-opaque-pointers/68179

The 'use-opaque-pointers' options, when enabled, changes the patterns to emit opaque pointers instead of typed pointers. As part of the migration effort the test have been converted to typed pointers, with an extra file for testing just typed pointers specific code paths.

Differential Revision: https://reviews.llvm.org/D144736