[llvm] [Attributor] Teach HeapToStack about conservative GC allocators (PR #113299)

[Shilei Tian via llvm-commits]

shiltian wrote:

I'm not sure. If the memory can be free at background, a pointer could be potentially not dereferenceable. That contradicts to the `IsAssumedNoFree` here, because this `nofree` means the pointer is still dereferenceable after the function call.

https://github.com/llvm/llvm-project/pull/113299