add pure-kotlin decoder #651

Job	Run time
Build and test cmake:gcc9	31s
Build and test cmake:clang15	1m 17s
Build and test cmake:clang15:asan	49s
Build and test cmake:clang15:tsan	1m 25s
Build and test cmake:clang15:ubsan	1m 17s
Build and test cmake:qemu-arm-neon-gcc	1m 38s
Build and test cmake-osx:clang	1m 6s
Build and test cmake-osx:gcc	1m 8s
Build and test cmake-win64:msvc-rel	1m 7s
Build and test cmake-win64:msvc-dbg	1m 31s
Build and test fuzz:clang15	32s
Build and test python3.10:clang15	1m 44s
Build and test python3.10-win	38s
Build and test maven	31s
Build and test bazel:root	32s
Build and test bazel:go	1m 4s
Build and test bazel:java	2m 11s
Build and test bazel:research	22s
Build and test bazel-osx:root	1m 15s
Build and test bazel-osx:go	1m 55s
Build and test bazel-osx:java	4m 50s
Build and test bazel-osx:research	1m 36s
Build and test bazel-win:root	1m 9s
Build and test bazel-win:java	4m 43s
Build and test bazel-win:research	1m 8s
	35m 59s

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