[PSA] Deprecation of gpu::Serialization* passes

The passes gpu-to-(cubin|hsaco) are now considered deprecated and have been removed from mlir-opt in favor of the GPU compilation attributes workflow; see the pull request. All new tests and significant contributions should use the new workflow.

Users can still enable these passes in mlir-opt using the CMake flag MLIR_ENABLE_DEPRECATED_GPU_SERIALIZATION; this option is there to diminish disruptions during the transition. However, these passes are going to be removed in a future release.

How can users migrate to the new workflow?
Substitute --gpu-to-(cubin|hsaco) for --(nvvm|rocdl)-attach-target, then add --gpu-module-to-binary after --gpu-to-llvm.

Traditional workflow:

mlir-opt gpu.mlir
  --convert-gpu-to-nvvm \ # --convert-gpu-to-rocdl
  --gpu-to-cubin        \ # --gpu-to-hsaco

New workflow:

mlir-opt gpu.mlir
  --convert-gpu-to-nvvm \ # --convert-gpu-to-rocdl
  --nvvm-attach-target  \ # --rocdl-attach-target
  --gpu-to-llvm         \