Analysis

[zachallaun]

Fixes #426

This PR introduces the concept of analysis, which is encapsulated by the %Lexical.Ast.Analysis{} struct. The idea is that, in the happy case, we can analyze the AST up front to capture important information and then re-use it for subsequent operations.

The most important new APIs/changes introduced:

• Lexical.Ast.analyze(document) - returns %Analysis{} which may or may not be valid (analysis.valid?). Used for whole-document analysis, e.g. indexing.
• Lexical.Ast.reanalyze_to(analysis, position) - returns %Analysis{} using the fragment of the original document up to the given position. Useful for things that may not require the whole document, e.g. resolving aliases. If the given analysis is already valid, this is a no-op.
• Lexical.Ast.Aliases has been removed in favor of analysis.
• Many Lexical.Ast functions have been refactored to also (or only) accept an analysis in place of a document.
• Added concept of derived data to Lexical.Document.Store. This allows for a derived analysis to be saved alongside the document and fetched using {:ok, %Document{}, %Analysis{}} = Document.Store.fetch(uri, :analysis).
• Refactored a number of existing LS features to use analysis, including entity resolution, completions, references.

---

Running the following extremely simple "benchmark" in iex -S mix:

# on main
iex> time fn -> Lexical.RemoteControl.Search.Indexer.create_index(project()); nil end
Time: 9.7 seconds

# on this branch
iex> time fn -> Lexical.RemoteControl.Search.Indexer.create_index(project()); nil end
Time: 1.8 seconds

[zachallaun]

Reminder to self: the pattern for detecting alias Foo, as: ... is incorrect, as other options can be passed as well, like warn: false.

edit: done

[zachallaun]

@scohen @scottming I'm going to mark this as ready for review, as I think it's very close to a merge-able state. I'll update the OP with some additional information.

[scohen]

This change is excellent.

I have a couple of small comments, but I think we should move forward on this.