Remove the "framework agnostic" step from the File Router

[Lodin]

Describe your motivation

The File System Router became fragile and produces a lot of bugs, so I suggest refactoring it to reduce the system complexity. We can get rid of the "framework agnostic" step where all the routes are created using pseudo-code which later is translated into the real React Router code. It would give us the proper view of React Router code and make it easier to debug.

Describe the solution you'd like

No response

Describe alternatives you've considered

No response

Additional context

No response

[platosha]

I'd suggest prototyping this and perhaps other ideas first.