Use std::optional if available. #1992

Job	Run time
PSV.Linux.22.04.gcc9.Tests.CodeCov	10m 52s
PSV.Linux.22.04.gcc9.Cpplint	8m 58s
PSV.Linux.22.04.gcc11	8m 25s
PSV.Linux.22.04.gcc9.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	2m 39s
PSV.Linux.22.04.gcc13	8m 53s
PSV.Win.VC2022	10m 45s
PSV.iOS.MacOS13.Xcode15	15m 50s
PSV.iOS.MacOS13.Xcode14	10m 18s
PSV.Linux.Android.22.04	5m 57s
PSV.Commit.Checker	5s
PSV.Linux.22.04.gcc11.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	2m 45s
PSV.MacOS15.Xcode16	4m 6s
PSV.Linux.latest.gcc14.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	2m 35s
PSV.Clang.Format.Checker	39s
PSV.Linux.22.04.clang	9m 6s
PSV.iOS.MacOS14.Xcode15	6m 9s
PSV.MacOS14.Xcode15	4m 20s
PSV.iOS.MacOS15.Xcode16	10m 7s
PSV.MacOS13.Xcode15.x86_64	3m 22s
	2h 5m 51s

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