Coretime Feature branch (relay chain) (#1694)

Also fixes: https://github.com/paritytech/polkadot-sdk/issues/1417

- [x] CoreIndex -> AssignmentProvider mapping will be able to change any
time.
- [x] Implement
- [x] Provide Migrations
- [x] Add and fix tests
- [x] Implement bulk assigner logic
- [x] bulk assigner tests
- [x] Port over current assigner to use bulk designer (+ share on-demand
with bulk): top-level assigner has core ranges: legacy, bulk
- [x] Adjust migrations to reflect new assigner structure
- [x] Move migration code to Assignment code directly and make it
recursive (make it possible to skip releases) -> follow up ticket.
- [x] Test migrations
- [x] Add migration PR to runtimes repo -> follow up ticket.
- [x] Wire up with actual UMP messages
- [x] Write PR docs

---------

Co-authored-by: eskimor <eskimor@no-such-url.com>
Co-authored-by: Bradley Olson <34992650+BradleyOlson64@users.noreply.github.com>
Co-authored-by: BradleyOlson64 <lotrftw9@gmail.com>
Co-authored-by: Anton Vilhelm Ásgeirsson <antonva@users.noreply.github.com>
Co-authored-by: antonva <anton.asgeirsson@parity.io>
Co-authored-by: Bastian Köcher <git@kchr.de>
Co-authored-by: Marcin S. <marcin@realemail.net>
Co-authored-by: Bastian Köcher <info@kchr.de>
Co-authored-by: command-bot <>

substrate/bin/node/runtime/src/lib.rs

@@ -1993,7 +1993,6 @@ impl OnUnbalanced<Credit<AccountId, Balances>> for IntoAuthor {
 }
 
 parameter_types! {
-	pub storage CoreCount: Option<CoreIndex> = None;
 	pub storage CoretimeRevenue: Option<(BlockNumber, Balance)> = None;
 }
 
@@ -2012,21 +2011,12 @@ impl CoretimeInterface for CoretimeProvider {
 		_end_hint: Option<u32>,
 	) {
 	}
-	fn check_notify_core_count() -> Option<u16> {
-		let count = CoreCount::get();
-		CoreCount::set(&None);
-		count
-	}
 	fn check_notify_revenue_info() -> Option<(u32, Self::Balance)> {
 		let revenue = CoretimeRevenue::get();
 		CoretimeRevenue::set(&None);
 		revenue
 	}
 	#[cfg(feature = "runtime-benchmarks")]
-	fn ensure_notify_core_count(count: u16) {
-		CoreCount::set(&Some(count));
-	}
-	#[cfg(feature = "runtime-benchmarks")]
 	fn ensure_notify_revenue_info(when: u32, revenue: Self::Balance) {
 		CoretimeRevenue::set(&Some((when, revenue)));
 	}