[llvm] [IR][TBAA] Allow multiple fileds with same offset in TBAA struct-path (PR #76356)

[Bushev Dmitry via llvm-commits]

dybv-sc wrote:

@dobbelaj-snps, I added few test cases both for old and for new struct-path featuring unions. During that I found a bug in my algorithm that is fixed now.
About those patch about !tbaa.metadata: I am not sure if that kind of metadata could be applied to unions. I'll look into that more closely and then will return with update. 

https://github.com/llvm/llvm-project/pull/76356