[llvm] Reapply "[MemProf] Streamline and avoid unnecessary context id duplication (#107918)" (PR #110036)

[Teresa Johnson via llvm-commits]

teresajohnson wrote:

@snehasish Note there are 2 commits here right now. The first is a straight reapply, the second contains the actual fixes and the test case.

https://github.com/llvm/llvm-project/pull/110036