Standalone `Colossus` repo

# Background

Currently, there is no easy way to discover or browse old versions of `Colossus`, and until very recently we did not do proper semantic release versioning or a change log. All of this is more important to get right as work on this software is going to start ramping up, and there may be multiple versions of the software running and being supported in the wild simultaneously. Also, as the number of contributors and users starts to increase, being able to do project management on the single monorepo will start to get cumbersome.

# Proposal

Create a new standalone repo for `Colossus`.

**Qs:**
- How do we deal with integration tests & CI in monorepo?
- How do we deal with integration tests & CI in this new repo?
- Do we need to factor out QN as well before this can be done?