Improve webpack config

[Shelob9]

1. Remove vue support - once [Feature] Move API key management for Pro and add-ons to main page. #3212 is done
2. Upgrade babel and webpack
3. Use @wordpress/scripts for the blocks compilation
4. Exclude React from our front-end builds and block-builds. Include React for our non block admin views.
5. HMR
6. Lazyloading
7. Include front client in admin client?

[Shelob9]

Builds should be:

• front -> edit client without React/wp. JSX transformed with wp.createElement load wp-* with wp_enqueue_scripts()
• front-legacy - edit client + legacy bundle. JSX transformed with wp.createElement. load wp-* with wp_enqueue_scripts()
• admin - render client + admin client. With React 16.8 and wp included. JSX transformed with React.createElement. Do NOT load wp-* with wp_enqueue_scripts()
• privacy - privacy client With React 16.8 and wp included. JSX transformed with React.createElement. Do NOT load wp-* with wp_enqueue_scripts()
• pro - Nothing, should go away for now, just keep old built files. Never change.