[clang] [CIR] Upstream extract op for VectorType (PR #138413)

[Henrich Lauko via cfe-commits]

xlauko wrote:

> As far as I understood, they will not always return ConstVecAttr and IntAttr because if an index or a vector is coming from parameters, or other variables, they are not constants in that case, and I am thinking even if the vector is constant, we will use load or get_global when we use it in Extract and will not pass it directly like const int 🤔, not sure if there is a case that will trigger that fold

Sorry my bad.

https://github.com/llvm/llvm-project/pull/138413