Separate role perms for "new" users

[Toastbrot236]

An instance owner should be able to configure a timespan after which a newly registered (and active) account is no longer considered "new". New accounts should have a separate set of configurable perms from regular users and trusted+ users, so an instance owner could, if they wanted to, set new users to have more restrictions. The API should also expose whether an account is considered to be new, since roles are already publicly exposed.

[Toastbrot236]

A question I had on this: Should unbanning/unrestricting a user (both manually and automatically) set them as new user or as regular user? Maybe configurable with a parameter if manually and by a config option if automatically? Should a user's "new" duration be tracked separately from their account age then?