add pure-kotlin decoder #638

Job	Run time
Build and test cmake:gcc9	28s
Build and test cmake:clang15	30s
Build and test cmake:clang15:asan	47s
Build and test cmake:clang15:tsan	48s
Build and test cmake:clang15:ubsan	50s
Build and test cmake:qemu-arm-neon-gcc	1m 3s
Build and test cmake-osx:clang	38s
Build and test cmake-osx:gcc	1m 5s
Build and test cmake-win64:msvc-rel	1m 7s
Build and test cmake-win64:msvc-dbg	1m 6s
Build and test fuzz:clang15	27s
Build and test python3.10:clang15	1m 43s
Build and test python3.10-win	45s
Build and test maven	32s
Build and test bazel:root	33s
Build and test bazel:go	1m 1s
Build and test bazel:java	42s
Build and test bazel:research	25s
Build and test bazel-osx:root	1m 21s
Build and test bazel-osx:go	1m 45s
Build and test bazel-osx:java	1m 43s
Build and test bazel-osx:research	1m 10s
Build and test bazel-win:root	1m 10s
Build and test bazel-win:java	3m 5s
Build and test bazel-win:research	51s
	25m 35s

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