[llvm] [SPIR-V] Add legalize-addrspace-cast pass (PR #137598)

[Nathan Gauër via llvm-commits]

Keenuts wrote:

> Why not using the existing address space inference pass ? It looks redundant

That's a good question, and reason was I didn't knew this existed. I just tried, the `llvm/test/CodeGen/SPIRV/pointers/pointer-addrspacecast.ll` test pass but `llvm/test/CodeGen/SPIRV/pointers/resource-addrspacecast.ll` don't.

I need to look into why the passes fails to infer the resource address spaces.

https://github.com/llvm/llvm-project/pull/137598