Hide nonce implementation details in metadata #6759

Job	Run time
preflight / preflight	33s
preflight / ci-versions	1m 23s
test-frame-ui	51m 3s
test-full-crypto-feature	2m 50s
cargo-check-all-crate-macos	11m 27s
cargo-check-benches (master)	20m 50s
cargo-check-benches (current)	26m 35s
test-node-metrics	14m 50s
cargo-check-each-crate (1)	49m 38s
cargo-check-each-crate (2)	44m 29s
cargo-check-each-crate (3)	20m 46s
cargo-check-each-crate (4)	45m 34s
cargo-check-each-crate (5)	54m 43s
cargo-check-each-crate (6)	26m 33s
cargo-check-each-crate (7)	50m 36s
test-frame-examples-compile-to-wasm	3m 8s
test-deterministic-wasm	8m 14s
check-tracing	2m 19s
check-metadata-hash	8m 20s
node-bench-regression-guard	14s
All test misc tests passed	1s
	7h 24m 6s

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