A* implementation #2164

Job	Run time
macos	2m 52s
formatting	46s
linux (linux-arm64-release, linux-arm64, qemu-aarch64-static)	1m 10s
linux (linux-sanitizer)	1m 33s
msvc (Release)	2m 49s
msvc (Debug)	2m 47s
linux (linux-amd64-release, linux-amd64)	49s
linux (linux-debug, valgrind --leak-check=full --error-exitcode=1)	44s
	13m 30s

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