Fix old checkpoint deletion by sorting the models properly

[Lordmau5]

Should fix #65 this time around.
The reason why this didn't work before is because it sorted them based on their name or time alone, but not also based on their prefix, so the resulting array looked like "G_", "D_", "G_", "D_", ...

This addresses that by also sorting based on their prefix, resulting in a properly sorted array "G_", "G_", "G_", "D_", "D_", "D_"

This has to be done this way due to how the itertools.groupby method works: https://note.nkmk.me/en/python-itertools-groupby/

Edit: Started training a new model from scratch with these code-changes, it's clearing it correctly

[codecov-commenter]

Codecov Report

Merging #89 (e6b5bf7) into main (9ffb621) will decrease coverage by 0.17%.
The diff coverage is 0.00%.

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@@            Coverage Diff             @@
##             main      #89      +/-   ##
==========================================
- Coverage   16.96%   16.80%   -0.17%     
==========================================
  Files          28       28              
  Lines        3359     3391      +32     
  Branches      385      393       +8     
==========================================
  Hits          570      570              
- Misses       2778     2810      +32     
  Partials       11       11              

Impacted Files	Coverage Δ
src/so_vits_svc_fork/utils.py	17.91% <0.00%> (-0.06%)	⬇️

... and 2 files with indirect coverage changes

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[34j]

Thanks for your PR. However, it needs to be modified as it cannot be merged if the ci (except codecov) is not passed. (Please run pre-commit.) Also, please use path.stem instead of .name as much as possible.

[34j]

@allcontributors add Lordmau5 bug, code

[allcontributors]

@34j

I've put up a pull request to add @Lordmau5! 🎉