Replace SPIR-V translator with LLVM SPIR-V backend

[kurapov-peter]

This is an umbrella ticked for LLVM SPIR-V backend enabling. As the backend matures and reaches non-experimental status, we can leverage it to eliminate the translator dependency. For the transition to run smoothly, we will stage the implementation alongside the translator approach until the backend reaches the same levels of functionality and performance. At its core, the transition for Triton will look like a localized change in how we produce SPIR-V from LLVM IR.

[etiotto]

In order to replace the LLVM-SPIRV translator we also need an issue to track the functional pass rate.

[pbchekin]

We have a GitHub workflow that can be triggered manually for a specific branch (added in #3392).
It is currently failing on main branch: https://github.com/intel/intel-xpu-backend-for-triton/actions/runs/13390267725.