Rococo/Westend Coretime Runtime

New runtimes for the Coretime Chain (a.k.a. "Broker Chain") described in
RFC-1.

Replaces https://github.com/paritytech/cumulus/pull/2889


- [x] Add Agile Coretime pallet
https://github.com/paritytech/substrate/pull/14568
- [x] Generate chain specs for local and testnets
- [x] Deploy parachain on Rococo - Done:
[rococo-coretime-rpc.polkadot.io](https://polkadot.js.org/apps/?rpc=wss%3A%2F%2Frococo-coretime-rpc.polkadot.io#/explorer)

DevOps issue for Aura keygen:
https://github.com/paritytech/devops/issues/2725

Edit (Dónal): This PR is mainly for Rococo, the Westend runtime is a
shell with no `Broker` pallet. The Rococo runtime has the broker calls
filtered for initial deployment.

---------

Co-authored-by: Dónal Murray <donal.murray@parity.io>
Co-authored-by: 0xmovses <r.v.melkonian@gmail.com>
Co-authored-by: Liam Aharon <liam.aharon@hotmail.com>
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 <>
Co-authored-by: Branislav Kontur <bkontur@gmail.com>

.gitlab/pipeline/build.yml

@@ -220,6 +220,7 @@ build-test-parachain:
 
 # DAG: build-runtime-assets -> build-runtime-collectives -> build-runtime-bridge-hubs
 # DAG: build-runtime-assets -> build-runtime-collectives -> build-runtime-contracts
+# DAG: build-runtime-assets -> build-runtime-coretime
 # DAG: build-runtime-assets -> build-runtime-starters -> build-runtime-testing
 build-runtime-assets:
   <<: *build-runtime-template
@@ -235,6 +236,15 @@ build-runtime-collectives:
     - job: build-runtime-assets
       artifacts: false
 
+build-runtime-coretime:
+  <<: *build-runtime-template
+  variables:
+    RUNTIME_PATH: "cumulus/parachains/runtimes/coretime"
+  # this is an artificial job dependency, for pipeline optimization using GitLab's DAGs
+  needs:
+    - job: build-runtime-assets
+      artifacts: false
+
 build-runtime-bridge-hubs:
   <<: *build-runtime-template
   variables: