Optimize keytablelist implementation #1451

Job	Run time
gcc-compile-with-bazel	11m 34s
gcc-compile-with-boringssl	12m 23s
gcc-compile-with-cmake	3m 22s
gcc-compile-with-cmake-all-options	5m 29s
gcc-compile-with-make	3m 12s
gcc-compile-with-make-all-options	4m 28s
clang-compile-with-bazel	10m 19s
clang-compile-with-bazel-all-options	10m 10s
clang-compile-with-boringssl	11m 6s
clang-compile-with-make	2m 46s
clang-compile-with-cmake	3m 22s
clang-compile-with-cmake-all-options	5m 2s
clang-compile-with-make-all-options	5m 5s
clang-unittest	15m 52s
gcc-compile-with-bazel-all-options	12m 5s
	1h 56m 15s

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