feat[cartesian]: Loops over data dimensions

[stubbiali]

This PR prototypes for-loops over data (i.e. static-sized) dimensions, easing the implementation of compute patterns ubiquitous in radiation and land surface parametrizations.

• Support is implemented for all backends.
• Allow calling functions from withing a for-loop and writing a for-loop within a function.
• Because fields with data dimensions must be allocated upfront, functions can now modify fields in-place and not return anything, so avoiding aliasing/copying larger high-dimensional arrays.

TODO:

• Unit tests

Ideas:

• Add new concept for functions without any return statement
• Allow defining higher-dimensional temporaries inside stencils