- Added ability to understand valid inserts, deletes and replacements for the `@functions` directive (and any other directive that uses our extensible code block bits).
- Added unit tests.
- Updated existing tests.
- Found an issue when completing some C# items the auto-completions would impact the underlying snapshot after we'd captured the change. Fixed this by forcing a reparse when we detect that our understanding of the latest snapshot and the actual latest snapshot diverge.
#2408
