feat: add missing require code action

[doorgan]

Closes #137

Adds an Add require for <module> code action.

Screen.Recording.2026-01-02.at.9.51.50.PM.mov

It uses these diagnostics to determine if the code action should be shown:

• You must require <module> before invoking the macro <module>.<fun>/<arity>
• <module>.<fun>/<arity> is undefined or private. However, there is a macro with the same name and arity. Be sure to require <module> if you intend to invoke this macro

There's also some minor refactors to generalize the Aliases logic to insert require directives and other directives we may want to add in this way