Restore outputlevel feature and test

[emstoudenmire]

This PR fixes the outputlevel feature of the network solvers codes. This parameter is now passed along with all the others as the region kwargs used to construct each RegionIterator. So now outputlevel is obtained through these keyword arguments.

The PR also adds some tests that the outputlevel feature works as expected.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 68.98%. Comparing base (beed105) to head (aa5134c).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #268      +/-   ##
==========================================
+ Coverage   68.53%   68.98%   +0.45%     
==========================================
  Files          81       81              
  Lines        4023     4024       +1     
==========================================
+ Hits         2757     2776      +19     
+ Misses       1266     1248      -18     

Flag	Coverage Δ
docs	0.00% <0.00%> (ø)

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