Skip internal keys' lookup in LRU for the DefaultCache. #1915

Job	Run time
PSV.Linux.22.04.gcc9.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	2m 17s
PSV.Linux.22.04.gcc9.Cpplint	8m 25s
PSV.Linux.22.04.gcc9.Tests.CodeCov	9m 59s
PSV.Linux.22.04.gcc13.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	6m 58s
PSV.Linux.22.04.gcc13	13m 12s
PSV.Linux.22.04.gcc11	7m 49s
PSV.MacOS14.Xcode15	4m 11s
PSV.Linux.22.04.clang	9m 14s
PSV.Linux.22.04.gcc11.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	2m 13s
PSV.MacOS13.Xcode16	5m 39s
PSV.iOS.MacOS13.Xcode15	10m 31s
PSV.Commit.Checker	9s
PSV.iOS.MacOS13.Xcode14	11m 49s
PSV.MacOS13.Xcode15.x86_64	3m 46s
PSV.Win.VC2019	10m 34s
PSV.Linux.Android.22.04	6m 12s
PSV.iOS.MacOS13.Xcode16	5m 29s
PSV.iOS.MacOS14.Xcode15	7m 41s
	2h 6m 8s

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