Use GUFuncWrapper for poly_fit. Added test for poly_fit

[iguinn]

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[codecov]

Codecov Report

❌ Patch coverage is 41.66667% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 63.04%. Comparing base (13f6306) to head (665a4d6).
⚠️ Report is 14 commits behind head on main.

Files with missing lines	Patch %	Lines
src/dspeed/processors/poly_fit.py	41.66%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #175      +/-   ##
==========================================
+ Coverage   62.72%   63.04%   +0.31%     
==========================================
  Files          59       59              
  Lines        3952     3953       +1     
==========================================
+ Hits         2479     2492      +13     
+ Misses       1473     1461      -12     

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