Add pallet referenda migration for referendumInfo

[nbaztec]

What does it do?

adds pallet referenda migration to v1. The migration was introduced in paritytech/substrate#12788 and was missing in the release notes and the correct labels. The ReferendumInfo type is migrated to the newer version to allow refunding deposits.

⚠️ Breaking Change ⚠️
The following invariants of ReferendumInfo - Approved, Rejected, Cancelled, TimedOut now have their second parameter optional, Option<Deposit<AccountId, Balance>>, which was previously Deposit<AccountId, Balance>.

• New event SubmissionDepositRefunded

SubmissionDepositRefunded {
	/// Index of the referendum.
	index: ReferendumIndex,
	/// The account who placed the deposit.
	who: T::AccountId,
	/// The amount placed by the account.
	amount: BalanceOf<T, I>,
},

• New error

/// The referendum status is invalid for this operation.
BadStatus

• New Extrinsic to refund submission deposit

refund_submission_deposit((index)