[llvm] Introduce DIExpressionOptimizer (PR #69769)

[Shubham Sandeep Rastogi via llvm-commits]

rastogishubham wrote:

Hi @pogo59 

It seems like `DIExpression::constantFold` only works on `DW_OP_LLVM_convert` operations. While this is folding mathematical expressions such as two `DW_OP_plus` in succession

https://github.com/llvm/llvm-project/pull/69769