Use more common terms than DMG, CGB, etc.

These are jargon that we do not *have* to use most of the time. It is worth acknowledging that they are terse and thus convenient to both read and write, but I think at least that “GBC” serves that purpose as well as “CGB” while being less confusing to a newcomer—and I remember my 2017 self being thusly confused!

We should nonetheless attempt to standardise on some terminology to talk about the relevant console groups (and, yes, this overlaps with #194). I wouldn't suggest using it verbatim, but I think [MTS' test naming](https://github.com/Gekkio/mooneye-test-suite/#test-naming) “groups” are an interesting starting point / food for thought.

Start by reading the terminology discussion in this issue, related issue #194, and MTS' test-naming reference. Inventory the current console-group terms and compare them with the proposed alternatives. Done means the project has an agreed terminology standard and the relevant documentation consistently reflects it.

Written by the indexing model from the issue text.