Training restarts at checkpoint instead of continuing

[TheTrustedComputer]

Describe the bug
This seems to be an unintentional regression. If one stops training mid-session and resumes, it starts from the beginning instead of continuing with the saved D and G checkpoints. The initial output shows these files aren't even loaded when they exist in the file system.

To Reproduce
Create any RVC model in the training tab, stop after the first checkpoint, and repeat, using the same parameters.

Expected behavior
Training should continue from the previously saved checkpoint, as RVC always has.

Screenshots
N/A

Desktop (please complete the following information):

• OS and version: Arch Linux
• Python version: 3.10.13
• Commit/Tag with the issue: main

Additional context
This is likely due to the commit 277eadc, which renamed checkpoint files from "2333333" to "latest". Resumption from the latest checkpoint worked in an older commit, but it's broken now.

[fumiama]

Maybe a digital epoch name is needed to resume in current code. We should modify the code and let the program check the name latest first.