CLI slice 1: settings, game version, index refresh, instances

[Maximilian-Nesslauer]

Part of #65, and the first pull request against #64.

Commands

Everything here has a Core operation on main or in an open pull request.

Command	Operation
borea settings show	IBoreaSettingsRepository.GetAsync
borea settings set game <dir>	IBoreaSettingsRepository.SaveAsync
borea settings set loader <id> <dir>	the loader map from #58
borea game version	the installed build from #57, and the master server's build from LatestVersionPing
borea index refresh	IContentIndexFetcher.FetchAsync from #60, reporting downloaded or not modified
borea instance list	IInstanceRepository.GetAllAsync, marking the active one
borea instance create <name>	CreateAsync with InstanceSource.Custom
borea instance rename, delete, activate	RenameAsync, DeleteAsync, SetActiveInstanceAsync
borea instance mods <instance>	the manifest entries in load order, GetEntriesAsync from #62
borea enable <id> --instance <name>, borea disable	IModStateRepository.SetActiveAsync and SetInactiveAsync

settings set comes first, because without it nothing can point the CLI at a game.

An instance is named on the command line by its display name, and by id when two names differ only in case.

Tests

One test per command, plus: no settings file, an instance name that is taken, an unknown instance, a disabled mod that stays disabled through enable of another mod.

Not in scope

Anything from the index beyond fetching it, and anything that writes a mod folder.

Depends on

#64, #57, #58, #60, #62.