Add broker pallet to coretime-westend (#3272)

This brings functionality to Westend's Coretime Chain runtime, where
previously it was not much more than a shell.

It is assumed that the Coretime pallet will have the same index in the
Westend runtime as it does in Rococo for the runtime calls.

TODO:
- [x] Generate chainspec
- [x] Regenerate weights
- [x] Check hardcoded RuntimeCall weights against relay weights for
transacts

Aura key generation: https://github.com/paritytech/devops/issues/2725

---------

Co-authored-by: command-bot <>
Co-authored-by: Bastian Köcher <git@kchr.de>
Co-authored-by: Anton Vilhelm Ásgeirsson <antonva@users.noreply.github.com>

substrate/frame/broker/src/mock.rs

@@ -77,7 +77,7 @@ pub struct TestCoretimeProvider;
 impl CoretimeInterface for TestCoretimeProvider {
 	type AccountId = u64;
 	type Balance = u64;
-	type RealyChainBlockNumberProvider = System;
+	type RelayChainBlockNumberProvider = System;
 	fn request_core_count(count: CoreIndex) {
 		CoreCountInbox::<Test>::put(count);
 	}