[libcxx-commits] [libcxx] [libc++] Implement ranges::iota (PR #68494)

[Konstantin Varlamov via libcxx-commits]

https://github.com/var-const requested changes to this pull request.

Almost LGTM -- please make sure all `constexpr`-capable tests also run in the non-constexpr mode, i.e. please make sure that all relevant tests follow the pattern of:
```
test();
static_assert(test());
```

https://github.com/llvm/llvm-project/pull/68494