Add MinDistanceSampling for 3D Ball

[JoshuaLampert]

Currently, MinDistanceSampling for a 3D Ball is not supported. To support it, there are two different options: 1. Properly support RegularDiscretization for a 3D Ball by adding Pyramid elements in the center similarly as in here and then use the fallback or 2. add a specialized method for Ball. This PR follows the second approach as it is quite straightforward to add, but allowing support for RegularDiscretization of a 3D Ball would still be nice (s.t. discretize(ball::Ball{𝔼{3}) could use that).

TODO:

• Add test

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.70%. Comparing base (e00e8b2) to head (7764ce9).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1121   +/-   ##
=======================================
  Coverage   87.70%   87.70%           
=======================================
  Files         191      191           
  Lines        5984     5986    +2     
=======================================
+ Hits         5248     5250    +2     
  Misses        736      736           

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[JoshuaLampert]

Would you mind creating a new release, @juliohm?

[juliohm]

Will do in a few seconds 👍🏽 Finishing up another PR with the getindex for topology as we discussed on Zulip.