Reland "Use native std::optional."

This is a reland of 490bb34b291593a964043d1d5f40ed766cf77555

Original change's description:
> Use native std::optional.
>
> Change-Id: I3bcf7a23eb27e98d24840b492930955125d35bd4
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/501476
> Reviewed-by: Brian Osman <brianosman@google.com>
> Reviewed-by: Ben Wagner <bungeman@google.com>
> Commit-Queue: John Stiles <johnstiles@google.com>

Change-Id: If14d35ed78905800b43b656f65bb17fc940e7770
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/502298
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
6 files changed