Use std::optional if available. #2027

Job	Run time
PSV.Linux.22.04.gcc9.Cpplint	8m 43s
PSV.Linux.22.04.gcc9.Tests.CodeCov	10m 4s
PSV.Linux.22.04.gcc9.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	2m 36s
PSV.iOS.MacOS14.Xcode15	6m 3s
PSV.Win.VC2022	10m 2s
PSV.Linux.22.04.gcc11	7m 59s
PSV.Linux.22.04.gcc11.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	2m 49s
PSV.Clang.Format.Checker	40s
PSV.MacOS14.Xcode15	3m 55s
PSV.MacOS13.Xcode15.x86_64	3m 9s
PSV.Linux.latest.gcc14.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	2m 29s
PSV.Linux.22.04.clang	8m 40s
PSV.iOS.MacOS15.Xcode16	5m 25s
PSV.iOS.MacOS13.Xcode15	14m 19s
PSV.iOS.MacOS13.Xcode14	12m 39s
PSV.Linux.Android.22.04	6m 16s
PSV.Commit.Checker	8s
PSV.Linux.22.04.gcc13	8m 38s
PSV.MacOS15.Xcode16	8m 25s
	2h 2m 59s

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