No Blockly instances need both Horizontal and Vertical flyouts. Dropping one of these saves 2 KB. Some don’t need flyouts at all (e.g. Blockly Games Puzzle or readonly documentation blocks).
This drops the compiled size by 25 kb if there are no categories. Which also indicates that the toolbox itself suffers from really bad bloat. The toolbox should not represent 1/6th of our codebase.
* Move fields and renderers into their own entry point so folks are able to be more selective about which fields and renderers they include in their bundle.