Improvements to JavaScript analysis

Changes to code extraction

Asynchronous generator methods are now parsed correctly and no longer cause a spurious syntax error.
Recognition of CommonJS modules has improved. As a result, some files that were previously extracted as global scripts are now extracted as modules.
Top-level await is now supported.
A bug was fixed in how the TypeScript extractor handles default-exported anonymous classes.
A bug was fixed in how the TypeScript extractor handles computed instance field names.