Better notebook markup renderer api (#121882)

* Better notebook markup renderer api

For #121256

- Use js modules for notebook output renderers
- Rename apis from `markdown` to `markup`
- Use imports and exports for apis instead of globals for apis
- Use esbuild instead of webpack so we can emit js modules
- Clearly split top level markup renderes from renderers that extend other renderers

* Use constant instead of comment for replacement