Add update channel for the update component

This PR will add an update channel for our update component which will allow for updates to the component to be distributed separate from a CMS release.

### Why?
If we were to ever have a repeat of what happened with 3.1.1 through 3.1.4 or in a rare instance where an update to the component was required in order to update the CMS, the update component would potentially fail when trying to update its own files.  Adding this update channel allows the update component to be updated with Joomla's integrated extension update mechanisms, which would not use the code in the update component, and provides a fallback in case of such an emergency.

### Testing Instructions
A new installation should have new database entries in the `#__update_sites` and `#__update_sites_extensions` table for this stream.  Upgraded installations should also get the channel but without known ID values (hence the subqueries in the update SQL files).  Updates on this channel will not work at this time, an XML file has not been provisioned at the coded location.