Linear length mult implementation

[ppinchuk]

Go from stepwise function to linear interpolation for length multiplier calculation.

Old is orange, new is blue:

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 98.03922% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 82.78%. Comparing base (1cadcc5) to head (0db14c2).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #214      +/-   ##
==========================================
+ Coverage   79.14%   82.78%   +3.64%     
==========================================
  Files         123      123              
  Lines       14064    14160      +96     
==========================================
+ Hits        11131    11723     +592     
+ Misses       2933     2437     -496     

Flag	Coverage Δ
unittests	82.78% <98.03%> (+3.64%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
reVX/config/least_cost_xmission.py	90.96% <100.00%> (+0.16%)	⬆️
reVX/least_cost_xmission/least_cost_xmission.py	90.00% <ø> (ø)
...eVX/least_cost_xmission/least_cost_xmission_cli.py	49.13% <100.00%> (+0.22%)	⬆️
tests/test_xmission_least_cost.py	95.32% <100.00%> (+0.06%)	⬆️
reVX/least_cost_xmission/trans_cap_costs.py	85.31% <95.45%> (+0.27%)	⬆️

... and 16 files with indirect coverage changes