Add Contract Equilibrium Utilities

[dpanici]

TODO

• [x] NO LONGER DOING, is not obvious/well-posed add expand utility (what should this be? should the current surface just be scaled to the larger rho? what about pressure/current/iota, should they be extrapolated? probably not)
• [x] Make contract utility initialize new equilibrium with Fourier Zernike coefficients such that the new surfaces are the same as the old
  • either through explicitly calculating the new coefficients
  • or through evaluating the R,Z, lambda of the old equilibrium in a volumetric grid that ends at the desired rho value, then passing those points into the new equilibrium for it to fit its new R,Z lambda
  • https://opg.optica.org/josaa/fulltext.cfm?uri=josaa-23-3-539&id=88096 try this formula
  • Ended up just doing a simple fit which works surprisingly well, |B| is exact when compared between the contracted and full eq, and |F| is the same to rtol of 1e-4
• [x] tests

Resolves #467