[MLIR][CUDA] Update export macros in CudaRuntimeWrappers (#73932)

This fixes a few issues present in the current version:
1) The macro doesn't enforce the default visibility on exported
   functions, causing compilation to fail when using
   `-fvisibility=hidden`
2) Not all functions are exported
3) Sometimes the macro ended up weirdly interleaved with `extern "C"`
   declarations