CreateConfig()
Also, remove nullable disable annotation for all using classes. Setting store can be nullable because `RulesetConfigManager()` can accept null setting store.
RealmContextFactory
RealmAccess
RulesetConfigCache
ShortName
ID
SettingsStore
Also fixes some remaining test failures due to locally constructed rulesets that are not being tracked by the game.
Will likely pull out that `RulesetConfigCache` next, but this is an "everything works" state.