add pure-kotlin decoder #649

Job	Run time
Build and test cmake:gcc9	35s
Build and test cmake:clang15	36s
Build and test cmake:clang15:asan	46s
Build and test cmake:clang15:tsan	49s
Build and test cmake:clang15:ubsan	1m 11s
Build and test cmake:qemu-arm-neon-gcc	58s
Build and test cmake-osx:clang	53s
Build and test cmake-osx:gcc	1m 4s
Build and test cmake-win64:msvc-rel	41s
Build and test cmake-win64:msvc-dbg	39s
Build and test fuzz:clang15	41s
Build and test python3.10:clang15	1m 41s
Build and test python3.10-win	52s
Build and test maven	40s
Build and test bazel:root	40s
Build and test bazel:go	1m 16s
Build and test bazel:java	2m 4s
Build and test bazel:research	22s
Build and test bazel-osx:root	59s
Build and test bazel-osx:go	2m 35s
Build and test bazel-osx:java	3m 33s
Build and test bazel-osx:research	1m 11s
Build and test bazel-win:root	1m 9s
Build and test bazel-win:java	4m 18s
Build and test bazel-win:research	1m 10s
	31m 23s

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