Switch to loops simple connectivity

[frheault]

Quick description

Simple improvement in speed for the simple connectivity, seems to be around 60sec. to 35sec. on my 700MB tractogram. Fix #1058
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Type of change

Check the relevant options.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Provide data, screenshots, command line to test (if relevant)

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Checklist

• My code follows the style guidelines of this project (run autopep8)
• I added relevant citations to scripts, modules and functions docstrings and descriptions
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I moved all functions from the script file (except the argparser and main) to scilpy modules
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[arnaudbore]

GTG

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.45%. Comparing base (5bcfd7f) to head (3918ffb).
Report is 53 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1082      +/-   ##
==========================================
- Coverage   69.45%   69.45%   -0.01%     
==========================================
  Files         447      447              
  Lines       24025    24048      +23     
  Branches     3280     3289       +9     
==========================================
+ Hits        16687    16702      +15     
- Misses       5943     5947       +4     
- Partials     1395     1399       +4     

Components	Coverage Δ
Scripts	70.24% <82.45%> (-0.02%)	⬇️
Library	68.38% <100.00%> (+0.01%)	⬆️