Support path to an image in log_image

[shcheklein]

Log image from an existing file. Helps to convert a repo like YOLO where images are produced already by some core code and we need to capture and transfer them into the DVCLive output dir.

It also adds some test for log_image.

Related: https://github.com/shcheklein/ultralytics
Related: ultralytics/ultralytics#1909

Docs treeverse/dvc.org#4463

---

• ❗ I have followed the Contributing to DVCLive guide.
• 📖 If this PR requires documentation updates, I have created a separate PR (or issue, at least) in dvc.org and linked it here.

Thank you for the contribution - we'll try to review it as soon as possible. 🙏

[codecov-commenter]

Codecov Report

Patch coverage: 96.15% and project coverage change: +0.03 🎉

Comparison is base (1cb31aa) 95.74% compared to head (311a124) 95.77%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #518      +/-   ##
==========================================
+ Coverage   95.74%   95.77%   +0.03%     
==========================================
  Files          41       41              
  Lines        2606     2630      +24     
  Branches      223      225       +2     
==========================================
+ Hits         2495     2519      +24     
  Misses         66       66              
  Partials       45       45              

Impacted Files	Coverage Δ
src/dvclive/plots/image.py	92.00% <66.66%> (+0.69%)	⬆️
src/dvclive/live.py	91.88% <100.00%> (+0.07%)	⬆️
tests/plots/test_image.py	100.00% <100.00%> (ø)

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[daavoo]

Minor comments about restructuring. I could do those myself in a follow-up

[shcheklein]

@daavoo I'll do those changes. Thanks for the review 🙏

[shcheklein]

@daavoo @dberenbaum I've addressed the review comments and created a doc update treeverse/dvc.org#4463

[shcheklein]

@daavoo can I do a release?

[daavoo]

@daavoo can I do a release?

sure

[shcheklein]

@daavoo do you draft them manually?

[daavoo]

@daavoo do you draft them manually?

Yes. https://github.com/iterative/dvclive/releases/new -> create a new version tag -> Generate release notes