Provide physical formulas for magnetic field calculations.

[kerrm]

The previous formulas for the magnetic field at the polar cap and light cylinder relied on a single scale. I replaced them with physical versions involving the neutron star moment of inertia, radius, etc., and using an explicit conversion units conversion appropriate for the cgs system. I updated the tests to agree with the new (exact) implementation. A few other lines were munged by black.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.78%. Comparing base (e14388c) to head (3ad5f9b).
Report is 369 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1858      +/-   ##
==========================================
+ Coverage   69.67%   69.78%   +0.11%     
==========================================
  Files         109      110       +1     
  Lines       25350    25579     +229     
  Branches     4500     4041     -459     
==========================================
+ Hits        17663    17851     +188     
- Misses       6564     6598      +34     
- Partials     1123     1130       +7     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[abhisrkckl]

Shall I merge this?