De-dupe inbound SCP traffic #6322

Job	Run time
rust-check-git-rev-deps	18s
fmt	16s
build (gcc, current)	1h 10m 54s
cargo-deny (advisories)	44s
build (gcc, current, --check-test-tx-meta)	57m 58s
cargo-deny (bans licenses sources)	47s
build (gcc, next)	1h 15m 38s
build (gcc, next, --check-test-tx-meta)	59m 55s
build (clang, current)	57m 48s
build (clang, current, --check-test-tx-meta)	50m 22s
build (clang, next)	1h 0m 18s
build (clang, next, --check-test-tx-meta)	51m 31s
complete	1s
	8h 6m 30s

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