Use an lru cache to drop duplicate beacons #1200

Job	Run time
hygiene	3m 0s
build (arm-unknown-linux-gnueabihf)	3m 24s
build (armv5te-unknown-linux-musleabi)	3m 37s
build (armv7-unknown-linux-musleabihf)	3m 28s
build (aarch64-unknown-linux-musl)	4m 7s
build (mips-unknown-linux-musl)	3m 47s
build (mipsel-unknown-linux-musl)	3m 36s
build (x86_64-unknown-debian-gnu)	3m 45s
build (x86_64-tpm-debian-gnu)	4m 36s
docker_buildx	9m 26s
release	0s
	42m 46s

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