Use pygit2 backend for fetch_refspecs

[karajan1001]

fixes: #8762
partly solves: #8477 and #8787
Improve the performance

Wait for treeverse/scmrepo#169

The performance improvement are shown in treeverse/scmrepo#169.

For the benchmark because the fetch operation only happens during temp or queue experiment running progress. We don't have this kind of benchmark and also hard to build one.

• ❗ I have followed the Contributing to DVC checklist.

• 📖 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]

Codecov Report

Base: 93.12% // Head: 93.33% // Increases project coverage by +0.21% 🎉

Coverage data is based on head (49a27f4) compared to base (97589a1).
Patch has no changes to coverable lines.

❗ Current head 49a27f4 differs from pull request most recent head 4b9fa61. Consider uploading reports for the commit 4b9fa61 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8907      +/-   ##
==========================================
+ Coverage   93.12%   93.33%   +0.21%     
==========================================
  Files         453      453              
  Lines       36600    36495     -105     
  Branches     5287     5278       -9     
==========================================
- Hits        34083    34062      -21     
+ Misses       2001     1917      -84     
  Partials      516      516              

Impacted Files	Coverage Δ
dvc/repo/update.py	48.64% <0.00%> (-2.87%)	⬇️
dvc/output.py	88.98% <0.00%> (ø)
dvc/config_schema.py	94.28% <0.00%> (ø)
tests/unit/remote/test_webdav.py	100.00% <0.00%> (ø)
dvc/repo/worktree.py	10.06% <0.00%> (+0.01%)	⬆️
dvc/testing/remote_tests.py	50.65% <0.00%> (+6.83%)	⬆️
dvc/testing/workspace_tests.py	73.85% <0.00%> (+7.18%)	⬆️

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[efiop]

For the benchmark because the fetch operation only happens during temp or queue experiment running progress. We don't have this kind of benchmark and also hard to build one.

Are there any manual results?

[karajan1001]

For the benchmark because the fetch operation only happens during temp or queue experiment running progress. We don't have this kind of benchmark and also hard to build one.

Are there any manual results?

The performance improvement are shown in treeverse/scmrepo#169.

This is from original.

This is after using pygit2 backend

[efiop]

Great work, @karajan1001 ! 🔥