<!-- Suggested PR title: Migrate PATH/TO/FILE.js to goog.module syntax -->

## The basics

- [ ] I branched from `goog_module`
- [ ] My pull request is against `goog_module`
- [ ] My code follows the [style guide](
      https://developers.google.com/blockly/guides/modify/web/style-guide)
- [ ] My code is presented in the form suggested in the [module
      conversion guide](https://github.com/google/blockly/issues/5026)
- [ ] I have run `npm test`.

## The details
### Resolves

Part of #5026

### Proposed Changes

Converts `PATH/TO/FILE.js` to `goog.module` with ES6 `const`/`let`.

### Additional Information

<!-- Anything else we should know? -->
