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

[Bushev Dmitry via llvm-commits]

dybv-sc wrote:

> From a glance at your implementation I assume you want to allow only the same offset to occur multiple times, but no other forms of overlap?
Yes, this is needed to support unions as struct path node.

I'll update LangRef then.

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