[Feature Request] Optional Dependencies

The ability to flag a listed dependency in modinfo as optional and not require it in order for the game to function. Of course this would only be used for non-synced things.

Start by locating the modinfo dependency handling and the validation path that distinguishes synced from non-synced features. Define how an optional dependency is represented, then verify that non-synced optional dependencies do not block the game while required and synced dependencies retain their existing behavior.

Written by the indexing model from the issue text.