add pure-kotlin decoder #654

Job	Run time
Build and test cmake:gcc9	31s
Build and test cmake:clang15	35s
Build and test cmake:clang15:asan	44s
Build and test cmake:clang15:tsan	44s
Build and test cmake:clang15:ubsan	49s
Build and test cmake:qemu-arm-neon-gcc	59s
Build and test cmake-osx:clang	35s
Build and test cmake-osx:gcc	41s
Build and test cmake-win64:msvc-rel	56s
Build and test cmake-win64:msvc-dbg	1m 8s
Build and test fuzz:clang15	33s
Build and test python3.10:clang15	2m 1s
Build and test python3.10-win	54s
Build and test maven	28s
Build and test bazel:root	29s
Build and test bazel:go	1m 6s
Build and test bazel:java	2m 16s
Build and test bazel:research	27s
Build and test bazel-osx:root	1m 35s
Build and test bazel-osx:go	1m 53s
Build and test bazel-osx:java	3m 11s
Build and test bazel-osx:research	1m 6s
Build and test bazel-win:root	1m 23s
Build and test bazel-win:java	5m 7s
Build and test bazel-win:research	1m 5s
	31m 16s

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