With the removal of mlir-vulkan-runner (as part of #73457) in
e7e3c45bc70904e24e2b3221ac8521e67eb84668, this pass no longer has to be
public (previously it had to be so the runner could use it). This commit
makes it instead only available for use by mlir-opt.
This is a recommit of 058d183980a2f334d085a46c32abded0557aa789 (#124301)
which had been reverted in 4573c857da88b3210d497d9a88a89351a74b5964 due
to a missing linker dependency on MLIRSPIRVTransforms in
mlir/test/lib/Pass/CMakeLists.txt (fixed in this commit).
With the removal of mlir-vulkan-runner (as part of #73457) in
e7e3c45bc70904e24e2b3221ac8521e67eb84668, this pass no longer has to be
public (previously it had to be so the runner could use it). This commit
makes it instead only available for use by mlir-opt.
