statement-distribution: prep for re-enabling (#4431)
In preparation for launching re-enabling (https://github.com/paritytech/polkadot-sdk/issues/2418), we need to adjust the disabling strategy of statement-distribution to use the relay parent's state instead of the latest state (union of active leaves). This will also ensure no raciness of getting the latest state vs accepting statements from disabling validators at the cost of being more lenient/potentially accepting more statements from disabled validators. - [x] PRDoc