[llvm] [SPIR-V] Rework usage of virtual registers' types and classes (PR #104104)

[Michal Paszkowski via llvm-commits]

michalpaszkowski wrote:

> Thank you @VyacheslavLevytskyy, this is a huge change and a very great progress, I can only imagine the time it took. The change looks good to me from the code perspective. However, please wait with merging for a couple of hours. I am running a full OpenCL CTS testing cycle + benchmarks and it should finish around your afternoon (I will add one more comment).

Confirming there are no regressions with OpenCL CTS

https://github.com/llvm/llvm-project/pull/104104