[llvm] [SPIR-V] Add SPIR-V structurizer (PR #97606)

[Michal Paszkowski via llvm-commits]

https://github.com/michalpaszkowski commented:

Thank you @Keenuts for the patch! I added some small nitpicky comments, but I think the patch looks great and is really easy to follow!

https://github.com/llvm/llvm-project/pull/97606