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/frame/broker/src/lib.rs

@@ -159,6 +159,10 @@ pub mod pallet {
 	pub type InstaPoolHistory<T> =
 		StorageMap<_, Blake2_128Concat, Timeslice, InstaPoolHistoryRecordOf<T>>;
 
+	/// Received core count change from the relay chain.
+	#[pallet::storage]
+	pub type CoreCountInbox<T> = StorageValue<_, CoreIndex, OptionQuery>;
+
 	#[pallet::event]
 	#[pallet::generate_deposit(pub(super) fn deposit_event)]
 	pub enum Event<T: Config> {
@@ -774,5 +778,13 @@ pub mod pallet {
 			Self::do_request_core_count(core_count)?;
 			Ok(())
 		}
+
+		#[pallet::call_index(19)]
+		#[pallet::weight(T::WeightInfo::notify_core_count())]
+		pub fn notify_core_count(origin: OriginFor<T>, core_count: CoreIndex) -> DispatchResult {
+			T::AdminOrigin::ensure_origin_or_root(origin)?;
+			Self::do_notify_core_count(core_count)?;
+			Ok(())
+		}
 	}
 }