add the ability to declare multiple impl blocks #9538

Job	Run time
preflight / preflight	43s
preflight / ci-versions	57s
cargo-check-benches (master)	20m 57s
test-full-crypto-feature	2m 35s
test-frame-ui	30m 2s
cargo-check-benches (current)	25m 36s
cargo-check-all-crate-macos	11m 43s
cargo-check-each-crate (1)	34m 21s
test-node-metrics	14m 15s
cargo-check-each-crate (2)	30m 50s
cargo-check-each-crate (3)	14m 51s
cargo-check-each-crate (4)	33m 40s
cargo-check-each-crate (5)	41m 2s
cargo-check-each-crate (6)	21m 44s
cargo-check-each-crate (7)	40m 21s
test-frame-examples-compile-to-wasm	2m 58s
test-deterministic-wasm	8m 17s
check-tracing	2m 13s
check-metadata-hash	7m 43s
node-bench-regression-guard	12s
All test misc tests passed	1s
	5h 45m 1s

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