Add `unstable-api` feature flag to `pallet-revive` #8300

Job	Run time
preflight / preflight	42s
preflight / ci-versions	1m 8s
cargo-check-benches (master)	20m 57s
cargo-check-benches (current)	20m 43s
test-frame-ui	27m 7s
test-full-crypto-feature	2m 29s
test-node-metrics	8m 6s
cargo-check-all-crate-macos	11m 21s
cargo-check-each-crate (1)	15m 53s
cargo-check-each-crate (2)	16m 51s
cargo-check-each-crate (3)	7m 37s
cargo-check-each-crate (4)	14m 41s
cargo-check-each-crate (5)	21m 14s
cargo-check-each-crate (6)	13m 15s
cargo-check-each-crate (7)	25m 2s
test-frame-examples-compile-to-wasm	2m 58s
test-deterministic-wasm	6m 7s
check-tracing	2m 13s
check-metadata-hash	5m 50s
node-bench-regression-guard	16s
All test misc tests passed	1s
	3h 44m 31s

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