[libcxx-commits] [libcxx] [libc++][NFC] Granularize includes of <optional> (PR #213433)

[Nikolas Klauser via libcxx-commits]

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philnik777 wrote:

We consider C++23 includes stable, so there should be
```c++
#if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 23
#  include <optional>
#endif
```
blocks at the end of the files where the include is removed.

https://github.com/llvm/llvm-project/pull/213433