Prototype splitting packages [2 days]

[yuriy-fix]

Based on https://github.com/vaadin/platform/issues/4936, prototype creation of the monorepo with the following structure:

• src (split and moved correspondingly under packages)
• packages
  • react-components
  • ... src files of the commercial components
  • ... dependencies from react-components-core
  • react-components-core
  • ... src files of the free components

Let's use npm workspaces and update package.json and repo scripts accordingly.

[tarekoraby]

On the naming of packages, a strong recommendation from the product team: Let's use,

• @vaadin/react-components for the free components
• @vaadin/react-components-pro for the pro components