Add Chilled event to staking chill extrinsics

[emostov]

closes #9242

This PR adds a Chilled(stash_account) event to chill_stash which is the underlying call used by the chill and chill_other extrinsic.

[emostov]

 left: `Event::Staking(Event::Chilled(14792786684846458762))`,
right: `Event::Staking(Event::Slash(14792786684846458762, 7000))`: Mismatch at: 0. Mismatching length. Got: 1803, expected: 1703', frame/offences/benchmarking/src/lib.rs:228:9

I need to fix this; error from tests in ci

[emostov]

Exact line of error:

substrate/frame/offences/benchmarking/src/lib.rs

Line 228 in 938e3a2

assert_eq!(a, b, "Mismatch at: {}. {}", idx, length_mismatch);

Chilled events probs need to get added somewhere here:

substrate/frame/offences/benchmarking/src/lib.rs

Lines 276 to 293 in 938e3a2

	let mut slash_events = raw_offenders.into_iter()
	.flat_map(|offender| {
	core::iter::once(offender.stash).chain(offender.nominator_stashes.into_iter())
	})
	.map(|stash| <T as StakingConfig>::Event::from(
	StakingEvent::<T>::Slash(stash, BalanceOf::<T>::from(slash_amount))
	))
	.collect::<Vec<_>>();
	let reward_events = reporters.into_iter()
	.flat_map(|reporter| vec![
	frame_system::Event::<T>::NewAccount(reporter.clone()).into(),
	<T as BalancesConfig>::Event::from(
	pallet_balances::Event::<T>::Endowed(reporter, (reward_amount / r).into())
	).into()
	]);
	// rewards are applied after first offender and it's nominators
	let slash_rest = slash_events.split_off(1 + n as usize);

[emostov]

bot merge

[ghost]

Trying merge.