Use std::optional if available. (#1623) #1989

Job	Run time
PSV.Linux.22.04.gcc9.Cpplint	8m 41s
PSV.Linux.22.04.gcc9.Tests.CodeCov	10m 22s
PSV.Linux.22.04.gcc13	8m 33s
PSV.iOS.MacOS13.Xcode15	12m 38s
PSV.Linux.22.04.gcc9.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	3m 2s
PSV.Linux.22.04.gcc11.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	3m 4s
PSV.Linux.Android.22.04	5m 52s
PSV.Linux.latest.gcc14.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	3m 27s
PSV.MacOS13.Xcode15.x86_64	6m 16s
PSV.MacOS14.Xcode15	4m 12s
PSV.iOS.MacOS13.Xcode14	15m 8s
PSV.Linux.22.04.clang	9m 28s
PSV.MacOS15.Xcode16	3m 9s
PSV.Linux.22.04.gcc11	8m 45s
PSV.iOS.MacOS14.Xcode15	5m 20s
PSV.Win.VC2022	9m 44s
PSV.iOS.MacOS15.Xcode16	6m 10s
PSV.Commit.Checker	0s
	2h 3m 51s

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