Clebsch field line coordinate functions

[unalmis]

New quantities used to compute some neoclassical quantities are moved here as requested at developer meeting.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.32%. Comparing base (f88c36c) to head (6d0ff50).
Report is 1800 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1102      +/-   ##
==========================================
+ Coverage   95.30%   95.32%   +0.02%     
==========================================
  Files          87       87              
  Lines       22166    22262      +96     
==========================================
+ Hits        21125    21221      +96     
  Misses       1041     1041              

Files with missing lines	Coverage Δ
desc/compute/_basis_vectors.py	100.00% <100.00%> (ø)
desc/compute/_core.py	100.00% <100.00%> (ø)
desc/compute/_field.py	100.00% <100.00%> (ø)
desc/compute/_metric.py	100.00% <100.00%> (ø)
desc/compute/data_index.py	97.05% <ø> (ø)

[github-actions]

|             benchmark_name             |         dt(%)          |         dt(s)          |        t_new(s)        |        t_old(s)        | 
| -------------------------------------- | ---------------------- | ---------------------- | ---------------------- | ---------------------- |
 test_build_transform_fft_lowres         |     +0.61 +/- 8.74     | +3.20e-03 +/- 4.59e-02 |  5.29e-01 +/- 4.3e-02  |  5.25e-01 +/- 1.7e-02  |
 test_build_transform_fft_midres         |     -0.09 +/- 3.03     | -5.25e-04 +/- 1.85e-02 |  6.12e-01 +/- 1.4e-02  |  6.12e-01 +/- 1.3e-02  |
 test_build_transform_fft_highres        |     -0.02 +/- 3.16     | -1.66e-04 +/- 3.18e-02 |  1.00e+00 +/- 1.5e-02  |  1.00e+00 +/- 2.8e-02  |
 test_equilibrium_init_lowres            |     +1.03 +/- 5.14     | +3.88e-02 +/- 1.94e-01 |  3.82e+00 +/- 1.0e-01  |  3.78e+00 +/- 1.6e-01  |
 test_equilibrium_init_medres            |     +0.23 +/- 3.79     | +9.76e-03 +/- 1.62e-01 |  4.27e+00 +/- 9.7e-02  |  4.26e+00 +/- 1.3e-01  |
 test_equilibrium_init_highres           |     +0.24 +/- 1.03     | +1.35e-02 +/- 5.83e-02 |  5.67e+00 +/- 3.9e-02  |  5.66e+00 +/- 4.3e-02  |
 test_objective_compile_dshape_current   |     -0.89 +/- 1.21     | -3.53e-02 +/- 4.79e-02 |  3.94e+00 +/- 3.0e-02  |  3.97e+00 +/- 3.7e-02  |
 test_objective_compile_atf              |     -0.65 +/- 3.12     | -5.54e-02 +/- 2.67e-01 |  8.50e+00 +/- 2.6e-01  |  8.56e+00 +/- 6.8e-02  |
 test_objective_compute_dshape_current   |     -2.37 +/- 3.89     | -3.10e-05 +/- 5.09e-05 |  1.28e-03 +/- 3.5e-05  |  1.31e-03 +/- 3.7e-05  |
 test_objective_compute_atf              |     -0.69 +/- 6.12     | -3.00e-05 +/- 2.65e-04 |  4.30e-03 +/- 1.6e-04  |  4.33e-03 +/- 2.1e-04  |
 test_objective_jac_dshape_current       |     +0.54 +/- 9.79     | +1.98e-04 +/- 3.61e-03 |  3.70e-02 +/- 1.5e-03  |  3.68e-02 +/- 3.3e-03  |
 test_objective_jac_atf                  |     -1.99 +/- 3.51     | -3.81e-02 +/- 6.71e-02 |  1.87e+00 +/- 4.0e-02  |  1.91e+00 +/- 5.4e-02  |
 test_perturb_1                          |     -1.07 +/- 2.05     | -1.53e-01 +/- 2.92e-01 |  1.41e+01 +/- 2.7e-01  |  1.42e+01 +/- 1.2e-01  |
 test_perturb_2                          |     -0.81 +/- 0.81     | -1.57e-01 +/- 1.57e-01 |  1.91e+01 +/- 1.3e-01  |  1.93e+01 +/- 9.3e-02  |
 test_proximal_jac_atf                   |     -0.77 +/- 1.21     | -5.76e-02 +/- 9.03e-02 |  7.39e+00 +/- 6.2e-02  |  7.45e+00 +/- 6.5e-02  |
 test_proximal_freeb_compute             |     -0.88 +/- 0.93     | -1.57e-03 +/- 1.67e-03 |  1.77e-01 +/- 1.1e-03  |  1.79e-01 +/- 1.3e-03  |
 test_proximal_freeb_jac                 |     +0.73 +/- 1.35     | +5.41e-02 +/- 1.00e-01 |  7.45e+00 +/- 7.5e-02  |  7.40e+00 +/- 6.6e-02  |
 test_solve_fixed_iter                   |     -0.53 +/- 6.13     | -9.77e-02 +/- 1.14e+00 |  1.84e+01 +/- 7.7e-01  |  1.85e+01 +/- 8.4e-01  |

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[dpanici]

add our notation in List of Vairables and that by default is rho theta zeta

[unalmis]

There is a resolution requirement for <|grad(rho)|> that was on ripple branch, but I forgot to add here. Corrected now.