[mlir][SPIRV] Enable use of opaque-pointers in spirv-cpu-runner

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

All passes required for lowering have already been successfully converted to allowing opaque-pointers. Switching the Spir-V runner to opaque-pointers is therefore only a matter of turning it on in these conversion passes. Regression tests also did not find any issues.

Differential Revision: https://reviews.llvm.org/D144725