Code Action: Add alias

[scohen]

When coding, it is more convenient to type what you mean, and then come back later and clean up things like aliases. This change implements a code action that understands your current editing context and adds aliases as you type. It finds suggestions using our fuzzy matcher (though it has a bit stricter fuzziness), then provides code actions for each suggestion.

It will fix the following alias types:

Foo.Bar.Baz| will result in aliases for modules similar to Baz %Foo.Bar.Baz|{} will result in aliases similar to Baz, but only those that have structs defined in them Foo.Bar.baz.function| will result in aliases for modules with a function with a name similar to function

This PR also pulled a bunch of common code out of orgaize_aliases and moved it to a code mod file, which resulted in organize_aliases having very little code left in it.

Fixes #716

[zachallaun]

Nice!

I don't have time to dig in at the moment, but a couple quick thoughts:

• In my opinion, an extra newline should be added after module-level aliases unless it's being added to an existing "block" of aliases. For example:

  defmodule Foo do
    alias Some.Newly.Added.Thing
  
    def example do
      Thing
    end
  end
  
  defmodule Bar do
    alias AAA.BBB.CCC
    alias Some.Newly.Added.Thing # no newline added because another alias was already present
    def example do
      Thing
    end
  end

• Where does the new alias get added when there are other module-level forms? like @moduledoc, defstruct, etc. IMO: Should be top of the module, but below @moduledoc with an extra newline.

  
  defmodule Foo do
    @moduledoc """
    Module doc for Foo
    """
  
    alias Some.Newly.Added.Thing
  
    def example do
      Thing
    end
  end

[scohen]

@zachallaun I actually think the newline should be added to the first condition to keep the existing formatting, agreed about where to place an initial alias, I'll write some tests for that.