v16: Expose the unstable metadata v16 #6406

Job	Run time
preflight / preflight	42s
preflight / ci-versions	1m 12s
cargo-check-benches (master)	21m 24s
cargo-check-benches (current)	24m 9s
test-frame-ui	46m 37s
cargo-check-all-crate-macos	11m 43s
test-full-crypto-feature	2m 45s
test-node-metrics	9m 48s
cargo-check-each-crate (1)	22m 30s
cargo-check-each-crate (2)	20m 41s
cargo-check-each-crate (3)	9m 54s
cargo-check-each-crate (4)	20m 39s
cargo-check-each-crate (5)	28m 29s
cargo-check-each-crate (6)	15m 8s
cargo-check-each-crate (7)	31m 30s
test-frame-examples-compile-to-wasm	3m 4s
test-deterministic-wasm	7m 53s
check-tracing	2m 21s
check-metadata-hash	7m 9s
node-bench-regression-guard	14s
All test misc tests passed	1s
	4h 47m 53s

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