Changes required for the React integration

[Janpot]

Bringing some of the changes on #3125 to master

• Make sure the top-level component can be imported server side (not rendered). And not fail on window not existing while initializing browser runtime. We can just error when trying to use the runtime instead.
• Avoid serverside rendering the react router. It's client side only
• Add interop for the Next.js image imports
• More decoupling of Toolpad project from the function runtime