* rename parachain-{upgrade -> system}
* Merge message-broker into parachain-system
* Remove message-broker and clean up
* Update docs
* Test upward messages sending
And also update the relay-sproof-builder so that it allows to set the
relay dispatch queue size for the given parachain.
* Test horizontal message sending
* Remove old inherent definitions
* Wait for block import in parachain consensus
There was a bug in the parachain consensus that when importing a relay
chain block that sets a new best parachain block, but the required
parachain block was not yet imported. This pr fixes this by waiting for
the block to be imported.
* Finish docs
Cecile Tonglet