[llvm] [ADT] Teach set_intersect to erase with iterators (PR #99569)

[Kazu Hirata via llvm-commits]

kazutakahirata wrote:

> I think my preference here would be to just always use the erase(iter) variant then. We can add back the erase(value) variant if we hit a use-case for it (and add test coverage for it then).

OK.  The latest iteration uses erase(iter) without checking `detail::HasMemberEraseIter<S1Ty>`.

https://github.com/llvm/llvm-project/pull/99569