Refactor transfer_complete_datasets for one transfer job

[Cadair]

fixes #339

[codecov]

Codecov Report

Attention: Patch coverage is 91.48936% with 4 lines in your changes missing coverage. Please review.

Project coverage is 97.55%. Comparing base (265e15d) to head (300fa04).

❗ Current head 300fa04 differs from pull request most recent head 7e2d45a

Please upload reports for the commit 7e2d45a to get more accurate results.

Files	Patch %	Lines
dkist/net/helpers.py	91.42%	3 Missing ⚠️
dkist/net/globus/transfer.py	90.90%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #340      +/-   ##
==========================================
+ Coverage   97.03%   97.55%   +0.52%     
==========================================
  Files          65       34      -31     
  Lines        4008     2005    -2003     
==========================================
- Hits         3889     1956    -1933     
+ Misses        119       49      -70     

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[codspeed-hq]

CodSpeed Performance Report

Merging #340 will not alter performance

_{Comparing Cadair:complete_datasets (451f37d) with main (983c1f1)}

Summary

✅ 9 untouched benchmarks

[SolarDrew]

Seems fine 👍