Teams should be renamed to something else (groups?)

[AlbertoPdRF]

We now have Committees/Teams, banned competitors, Officers, and soon Councils (#3884) all handled as teams on the website, which is confusing and error-prone. Renaming teams to groups and a bit of clean up seems necessary at this point.

[jfly]

I like the term "group", it only potentially conflicts with "google group", and I think that's a manageable bit of confusion.

[danieljames-dj]

Assigned this to myself because I'm already working on this. The discussion on the model of groups (or rather user_groups) can be found here: https://github.com/thewca/worldcubeassociation.org/issues/8122.