Implement Brioche.glob global function

[kylewlacy]

This PR adds support for a new Brioche.glob global function. The core idea is very similar to Brioche.includeFile / Brioche.includeDirectory (#34 / #35): the project analyzer recognizes calls to Brioche.glob, looks at the local filesystem, then builds a recipe that can be retrieved with a special op from the JS side. See brioche-dev/brioche-packages#10 for the implementation in std

Here's an example:

// myproject/
//   project.bri
//   Cargo.toml
//   Cargo.lock
//   src/
//     main.rs
import * as std from "std";

// Returns a directory artifact with these entries:
//   Cargo.toml
//   Cargo.lock
//   src/
//     main.rs
export default async () => {
  return Brioche.glob("Cargo.lock", "Cargo.toml", "src");
};

Glob patterns are matched using the walkdir and globset crates (glob patterns are built with the options literal_separator, backslash_escape, and empty_alternates)