Fixes bugs in regrid-xy, restore original directory structure

[mlee03]

Describe your changes

This PR restores the original directory structure where

1. work_dir is the working directory containing the extracted grid_spec.nc, mosaic, and grid files from the grid_spec tarfile.
2. remap_dir is the directory containing the remap files that are either generated or reused during the regridding workflow.

These directories remove the need to move and copy relevant files before fregrid is invoked.

This PR still requires changes to fre-workflow and requires testing within the workflow

Issue ticket number and link (if applicable)

#609

Checklist before requesting a review

• I ran my code
• I tried to make my code readable
• I tried to comment my code
• I wrote a new test, if applicable
• I wrote new instructions/documentation, if applicable
• I ran pytest and inspected it's output
• I ran pylint and attempted to implement some of it's feedback
• No print statements; all user-facing info uses logging module

[codecov]

Codecov Report

❌ Patch coverage is 91.22807% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.74%. Comparing base (b287d62) to head (7d8d148).
⚠️ Report is 204 commits behind head on main.

Files with missing lines	Patch %	Lines
fre/app/regrid_xy/regrid_xy.py	90.38%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #617      +/-   ##
==========================================
+ Coverage   73.67%   73.74%   +0.06%     
==========================================
  Files          65       65              
  Lines        4175     4178       +3     
==========================================
+ Hits         3076     3081       +5     
+ Misses       1099     1097       -2     

Flag	Coverage Δ
unittests	73.74% <91.22%> (+0.06%)	⬆️

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[ilaflott]

largely looks good, but i'm concerned the os.chdir isn't as transient as we need it to be.

[mlee03]

Remember to finish reviewing this PR 😁

[ilaflott]

I know @mlee03 appreciates a thorough review, so i took more time to be more thorough!

[mlee03]

additional change that will come, the f-strings will be changed to use %s for the logger

[singhd789]

All my comments look like they're addressed and the tests pass! Wooo, good job. I'd just say merge in main and we're good to go.