cylindrical coordinates

[ddudt]

New grid and basis classes for working in cylindrical coordinates $(R,\phi,Z)$. This is required for the PlasmaField class introduced in #996. This PR isolates those changes from that original PR to aid review.

The order of these related PRs are:

1. New Grid API #2053 dd/grids
2. cylindrical coordinates #2253 dd/cylindrical
3. Biot-Savart volume integral #996 dd/B_plasma
4. BMW and FIELDLINES-style output formatting for B_plasma calculations #1883 ma/bmw_format
5. TBD new divertor objectives

To-Do:

• copy over CylindricalGrid class, and update to new API
• copy over cylindrical grids tests and/or add new tests

[maya-avida]

More to-dos:

• add symmetry?
• add real space bounds to easily rescale nodes to physical space
• generalized fft and dct attributes
• generalized transforms

[maya-avida]

Should this be RpZ or rpz?

[ddudt]

Good catch, we probably want "RpZ" to distinguish from rho and zeta

[YigitElma]

@maya-avida, if you run the following, the formatting checks/fixes will happen automatically every time you commit something.

pip install pre-commit
pre-commit install

These and some other useful instructions can be found on the Contributing Guide.