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>

prdoc/pr_3272.prdoc

@@ -0,0 +1,11 @@
+# Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
+# See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
+
+title: Westend Coretime Runtime
+
+doc:
+  - audience: Runtime User
+    description: |
+      Add the Broker pallet to the Westend Coretime Chain runtime for the main functionality and sales to start.
+
+crates: [ ]