models/default_versions: Add async fn variants

[Turbo87]

I hate the duplication... but it'll be gone soon!

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 26 lines in your changes missing coverage. Please review.

Project coverage is 89.18%. Comparing base (c9d7cbf) to head (041c456).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
src/models/default_versions.rs	0.00%	15 Missing ⚠️
src/bin/crates-admin/default_versions.rs	0.00%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10036      +/-   ##
==========================================
- Coverage   89.22%   89.18%   -0.04%     
==========================================
  Files         295      295              
  Lines       30836    30847      +11     
==========================================
- Hits        27514    27512       -2     
- Misses       3322     3335      +13     

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