Add and test events in `pallet-conviction-voting` #6310

Job	Run time
preflight / preflight	32s
preflight / ci-versions	1m 7s
cargo-check-all-crate-macos	11m 10s
cargo-check-benches (master)	21m 14s
cargo-check-benches (current)	24m 16s
cargo-check-each-crate (1)	22m 46s
cargo-check-each-crate (2)	20m 41s
test-frame-ui	46m 44s
cargo-check-each-crate (3)	9m 45s
cargo-check-each-crate (4)	24m 15s
cargo-check-each-crate (5)	30m 4s
test-full-crypto-feature	2m 39s
cargo-check-each-crate (6)	15m 10s
test-node-metrics	10m 52s
cargo-check-each-crate (7)	32m 1s
test-frame-examples-compile-to-wasm	3m 5s
test-deterministic-wasm	8m 1s
check-tracing	2m 21s
check-metadata-hash	7m 14s
node-bench-regression-guard	17s
All test misc tests passed	1s
	4h 54m 15s

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