Skip internal keys' lookup in LRU for the DefaultCache. #1897

Job	Run time
PSV.MacOS14.Xcode15	4m 10s
PSV.Linux.22.04.gcc9.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	2m 25s
PSV.Linux.22.04.gcc11.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	2m 6s
PSV.Linux.22.04.gcc9.Cpplint	8m 40s
PSV.Linux.22.04.gcc13	20m 25s
PSV.Linux.22.04.clang	9m 9s
PSV.Linux.22.04.gcc13.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	8m 56s
PSV.Commit.Checker	6s
PSV.Linux.Android.22.04	6m 2s
PSV.Linux.22.04.gcc9.Tests.CodeCov	5m 30s
PSV.MacOS13.Xcode15.x86_64	5m 34s
PSV.iOS.MacOS13.Xcode16	5m 18s
PSV.iOS.MacOS14.Xcode15	8m 27s
PSV.Linux.22.04.gcc11	8m 8s
PSV.iOS.MacOS13.Xcode14	10m 30s
PSV.iOS.MacOS13.Xcode15	10m 14s
PSV.Win.VC2019	9m 19s
PSV.MacOS13.Xcode16	4m 10s
	2h 9m 9s

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