This commit adds CJS/ESM interoperability when running in --compat mode.
Before executing files, they are analyzed and all CommonJS modules are
transformed on the fly to a ES modules. This is done by utilizing analyze_cjs()
functionality from deno_ast. After discovering exports and reexports, an ES
module is rendered and saved in memory for later use.
There's a caveat that all files ending with ".js" extension are considered as
CommonJS modules (unless there's a related "package.json" with "type": "module").
