Get lobby announcement from Atlas

[ASpoonPlaysGames]

Marking as a draft because this relies on a new Atlas endpoint. (R2Northstar/Atlas#38)

[ASpoonPlaysGames]

This was done to avoid having to override ui/_menus.nut in Northstar.Custom as well.
I could have done the HTTP stuff in Launcher, but that then splits this feature into 3 PRs :/

Unfortunately this does mean that clients who have Northstar.Custom disabled will not see the announcements. This makes up a tiny proportion of the playerbase, so personally I'm not too concerned.

[Alystrasz]

• How do you consider displaying this information in the lobby?
• Do you plan on opening the Atlas PR yourself?

[ASpoonPlaysGames]

• How do you consider displaying this information in the lobby?

It's already done and has been for a while, all you need to do is set some convars to display a message. Currently we display a message about progression.

• Do you plan on opening the Atlas PR yourself?

No, I haven't touched Go before really. It would basically be the same as mainmenupromos though, perhaps with a localisation file sent in some way as well? Idk.

The linked issue details requirements.