Migrate Staking pallet to v13 (#6365)

* add staking v13 migration

* add migration to polkadot

* only migrate staking

* un-remove other migrations

* fmt

* retrigger ci

* cargo update -p sp-io

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: parity-processbot <>
Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>