[llvm] [SPIRV] Add a `SPIRVTypeInst` type with some guardrails (PR #179947)

[Juan Manuel Martinez Caamaño via llvm-commits]

jmmartinez wrote:

I'll do one test next week were I replace as much as possible of `SPIRVType` with `SPIRVTypeInst` and see what happens.

https://github.com/llvm/llvm-project/pull/179947