Add point B measurement error objective

[dpanici]

• Adds objective for B measurements at points (outside the plasma, though this is not something I check for explicitly, it just does not make sense if plasma currents are present as the virtual casing principle will get the plasma contribution incorrect).

• change print value to be more intuitive for this objective (show error in matching targets, not just the compute value)

[github-actions]

|             benchmark_name             |         dt(%)          |         dt(s)          |        t_new(s)        |        t_old(s)        | 
| -------------------------------------- | ---------------------- | ---------------------- | ---------------------- | ---------------------- |
 test_build_transform_fft_lowres         |     -3.99 +/- 5.12     | -2.25e-02 +/- 2.89e-02 |  5.42e-01 +/- 2.0e-02  |  5.64e-01 +/- 2.1e-02  |
 test_equilibrium_init_medres            |     +1.70 +/- 4.56     | +7.43e-02 +/- 2.00e-01 |  4.45e+00 +/- 1.1e-01  |  4.38e+00 +/- 1.7e-01  |
 test_equilibrium_init_highres           |     -0.01 +/- 2.18     | -6.69e-04 +/- 1.21e-01 |  5.56e+00 +/- 1.1e-01  |  5.56e+00 +/- 5.1e-02  |
 test_objective_compile_dshape_current   |     -0.07 +/- 1.16     | -2.86e-03 +/- 4.56e-02 |  3.94e+00 +/- 2.1e-02  |  3.95e+00 +/- 4.1e-02  |
 test_objective_compute_dshape_current   |     -0.83 +/- 2.32     | -2.94e-05 +/- 8.20e-05 |  3.50e-03 +/- 5.7e-05  |  3.53e-03 +/- 5.9e-05  |
 test_objective_jac_dshape_current       |     +1.14 +/- 8.48     | +4.66e-04 +/- 3.47e-03 |  4.13e-02 +/- 3.0e-03  |  4.09e-02 +/- 1.7e-03  |
 test_perturb_2                          |     +1.19 +/- 2.74     | +2.35e-01 +/- 5.41e-01 |  2.00e+01 +/- 3.9e-01  |  1.97e+01 +/- 3.8e-01  |
 test_proximal_freeb_jac                 |     +0.93 +/- 1.28     | +6.83e-02 +/- 9.45e-02 |  7.44e+00 +/- 6.1e-02  |  7.37e+00 +/- 7.2e-02  |
 test_solve_fixed_iter                   |     -0.89 +/- 1.81     | -2.58e-01 +/- 5.25e-01 |  2.87e+01 +/- 3.7e-01  |  2.90e+01 +/- 3.8e-01  |
 test_LinearConstraintProjection_build   |     -0.46 +/- 1.30     | -1.05e-01 +/- 2.98e-01 |  2.29e+01 +/- 1.5e-01  |  2.30e+01 +/- 2.6e-01  |
 test_build_transform_fft_midres         |     +0.73 +/- 4.48     | +4.45e-03 +/- 2.74e-02 |  6.16e-01 +/- 2.1e-02  |  6.11e-01 +/- 1.8e-02  |
 test_build_transform_fft_highres        |     -0.74 +/- 2.35     | -7.27e-03 +/- 2.31e-02 |  9.77e-01 +/- 1.2e-02  |  9.84e-01 +/- 2.0e-02  |
 test_equilibrium_init_lowres            |     -0.07 +/- 2.21     | -2.82e-03 +/- 8.63e-02 |  3.91e+00 +/- 5.3e-02  |  3.91e+00 +/- 6.8e-02  |
 test_objective_compile_atf              |     -0.21 +/- 4.84     | -1.69e-02 +/- 3.89e-01 |  8.02e+00 +/- 2.9e-01  |  8.04e+00 +/- 2.6e-01  |
 test_objective_compute_atf              |     +1.87 +/- 2.79     | +1.91e-04 +/- 2.86e-04 |  1.04e-02 +/- 2.0e-04  |  1.02e-02 +/- 2.0e-04  |
 test_objective_jac_atf                  |     -1.02 +/- 1.45     | -2.01e-02 +/- 2.87e-02 |  1.96e+00 +/- 2.3e-02  |  1.98e+00 +/- 1.7e-02  |
 test_perturb_1                          |     +0.04 +/- 1.75     | +5.85e-03 +/- 2.51e-01 |  1.43e+01 +/- 8.0e-02  |  1.43e+01 +/- 2.4e-01  |
 test_proximal_jac_atf                   |     -0.45 +/- 0.70     | -3.72e-02 +/- 5.78e-02 |  8.20e+00 +/- 4.7e-02  |  8.24e+00 +/- 3.3e-02  |
 test_proximal_freeb_compute             |     +0.49 +/- 1.07     | +9.68e-04 +/- 2.12e-03 |  1.98e-01 +/- 1.6e-03  |  1.97e-01 +/- 1.3e-03  |
 test_solve_fixed_iter_compiled          |     +0.01 +/- 0.74     | +1.13e-03 +/- 1.25e-01 |  1.70e+01 +/- 6.7e-02  |  1.70e+01 +/- 1.1e-01  |

[codecov]

Codecov Report

Attention: Patch coverage is 87.91209% with 11 lines in your changes missing coverage. Please review.

Project coverage is 95.53%. Comparing base (8048085) to head (194e489).

Files with missing lines	Patch %	Lines
desc/objectives/_reconstruction.py	87.20%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1436      +/-   ##
==========================================
- Coverage   95.56%   95.53%   -0.04%     
==========================================
  Files          98       99       +1     
  Lines       25115    25203      +88     
==========================================
+ Hits        24001    24077      +76     
- Misses       1114     1126      +12     

Files with missing lines	Coverage Δ
desc/magnetic_fields/_current_potential.py	99.39% <100.00%> (+<0.01%)	⬆️
desc/objectives/__init__.py	100.00% <100.00%> (ø)
desc/objectives/_reconstruction.py	87.20% <87.20%> (ø)

... and 1 file with indirect coverage changes