Skip internal keys' lookup in LRU for the DefaultCache. #1918

Job	Run time
PSV.Linux.22.04.gcc9.Tests.CodeCov	10m 1s
PSV.Linux.22.04.gcc9.Cpplint	8m 11s
PSV.Linux.22.04.gcc11.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	2m 25s
PSV.Linux.22.04.gcc9.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	2m 18s
PSV.MacOS13.Xcode15.x86_64	4m 11s
PSV.Linux.Android.22.04	5m 37s
PSV.Linux.22.04.gcc13	13m 10s
PSV.Linux.22.04.clang	8m 41s
PSV.MacOS15.Xcode16	5m 37s
PSV.iOS.MacOS13.Xcode14	17m 36s
PSV.Linux.22.04.gcc11	7m 46s
PSV.MacOS14.Xcode15	3m 48s
PSV.iOS.MacOS13.Xcode15	11m 3s
PSV.Linux.latest.gcc14.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	2m 16s
PSV.Commit.Checker	14s
PSV.iOS.MacOS15.Xcode16	9m 17s
PSV.Win.VC2022	10m 33s
PSV.iOS.MacOS14.Xcode15	7m 7s
	2h 9m 51s

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