add pure-kotlin decoder #658

Job	Run time
Build and test cmake:gcc9	30s
Build and test cmake:clang15	33s
Build and test cmake:clang15:asan	43s
Build and test cmake:clang15:tsan	48s
Build and test cmake:clang15:ubsan	48s
Build and test cmake:qemu-arm-neon-gcc	1m 3s
Build and test cmake-osx:clang	48s
Build and test cmake-osx:gcc	35s
Build and test cmake-win64:msvc-rel	1m 2s
Build and test cmake-win64:msvc-dbg	50s
Build and test fuzz:clang15	1m 5s
Build and test python3.10:clang15	3m 30s
Build and test python3.10-win	36s
Build and test maven	23s
Build and test bazel:root	1m 8s
Build and test bazel:go	1m 2s
Build and test bazel:java	2m 13s
Build and test bazel:research	1m 14s
Build and test bazel-osx:root	1m 36s
Build and test bazel-osx:go	1m 50s
Build and test bazel-osx:java	6m 28s
Build and test bazel-osx:research	1m 1s
Build and test bazel-win:root	56s
Build and test bazel-win:java	3m 28s
Build and test bazel-win:research	1m 17s
	35m 27s

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