feat: Introduce a generator based samples

[demirkayaender]

Current samples are written as if they were project files: There's a complex file structure, significant code reuse etc.
However, since samples are for education, we need to contain everything for a sample inside a single folder so the user can see all the elements in one place.
This PR creates a hello world sample using this logic. We will continue with other samples following the same template and remove them eventually.

To view how they look, see: https://github.com/demirkayaender/cadence-samples/tree/hello_world/new_samples/hello_world