[Feature Request] package classes/enums

As far as I'm aware it's currently not possible to specify a class/enum/alias as only visible to current file. This feature is already implemented for functions and fields; it would be amazing to have other kinds of definitions also implement this behavior.

Start by locating the existing implementation and tests for file-only visibility on functions and fields in the Lua language server. Trace how class, enum, and alias definitions are represented, then define the matching behavior for those definitions. Done means all three kinds support the same current-file visibility behavior with coverage for the relevant cases.

Written by the indexing model from the issue text.