[libcxx-commits] [libcxx] [libc++] Decouple `optional<T>` and `optional<T&>` base classes (PR #215012)

[William Tran-Viet via libcxx-commits]

================

----------------
smallp-o-p wrote:

IIUC, this refactoring also lets us directly inline the iterator functions into `optional<T>`, since this was meant to handle the `optional<T&>` case, which no longer applies. Could go in this change or as another follow-up.

https://github.com/llvm/llvm-project/pull/215012