Assembler: Add option for server only version

[Cleptomania]

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[Cleptomania]

The option is there now, though it needs fleshed out a bit more. Right now it just ignores client side mods(this has some conflict with the caching of mod downloads though, if a client only mod is cached, and you don't force download, it will be included).

Downloading mods from CurseForge makes this kind of annoying to deal with because of having to dynamically fetch the filename from the Curse API. To deal with this in the GitHub actions build I just do the server build first, so that it doesn't have a mod download cache. There could technically be server only mods included, but there aren't right now, and I doubt there will be.

Probably not worth making that better until either we have nothing being downloaded from curseforge directly(unlikely) or we have a better caching system(intermediate self-hosted cache that can be manually triggered to update as needed? Only really needed for the Curse mods, pulling JARs from Github is fine).