No PRF convolution applied to ePSFs

[t-brandt]

This is currently a draft PR to implement the appropriate treatment of convolutions when an ePSF is supplied.

[codecov]

Codecov Report

❌ Patch coverage is 89.13043% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.94%. Comparing base (d18949b) to head (7ac6233).
⚠️ Report is 19 commits behind head on main.

Files with missing lines	Patch %	Lines
romanisim/psf.py	90.24%	4 Missing ⚠️
romanisim/image.py	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #357      +/-   ##
==========================================
- Coverage   89.63%   84.94%   -4.69%     
==========================================
  Files          17       31      +14     
  Lines        2633     3633    +1000     
==========================================
+ Hits         2360     3086     +726     
- Misses        273      547     +274     

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