[llvm] [CodeExtractor][Verifier] Fix OoB read when a DIExpression is used multiple times (PR #226857)

[Henry Jiang via llvm-commits]

https://github.com/mustartt approved this pull request.

As a direct fix for the out of bound read for https://github.com/llvm/llvm-project/pull/224360 this looks good to me, as well as the verifier. 
Let's create an issue to outlined shared case explicitly.

https://github.com/llvm/llvm-project/pull/226857