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

[Nikita Popov via llvm-commits]

nikic wrote:

> Existing tests cover the new code path. Somewhat worrying is that the
existing "erase-by-value" code path is no longer covered. I am not
aware of any container that has erase(value) but not remove_if or
erase(iter).

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).

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