perf: try pread like zarrs's use of File::read_exact_at

[ilan-gold]

After our conversation on Wednesday, I got to thinking more about what zarr-python doesn't do that zarrs, for example, does and this came to mind.

TODO:

• Add unit tests and/or doctests in docstrings
• Add docstrings and API docs for any new/modified user-facing classes and functions
• New/modified features documented in docs/user-guide/*.md
• Changes documented as a new file in changes/
• GitHub Actions have all passed
• Test coverage is 100% (Codecov passes)

[codecov]

Codecov Report

❌ Patch coverage is 62.06897% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.45%. Comparing base (b871a22) to head (72cb294).

Files with missing lines	Patch %	Lines
src/zarr/storage/_local.py	62.06%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4039      +/-   ##
==========================================
- Coverage   93.53%   93.45%   -0.09%     
==========================================
  Files          88       88              
  Lines       11894    11912      +18     
==========================================
+ Hits        11125    11132       +7     
- Misses        769      780      +11     

Files with missing lines	Coverage Δ
src/zarr/storage/_local.py	92.79% <62.06%> (-4.46%)	⬇️

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[codspeed-hq]

Merging this PR will not alter performance

✅ 66 untouched benchmarks
⏩ 6 skipped benchmarks¹

---

_{Comparing ig/pread (72cb294) with main (6ce787d)²}

Footnotes

1. 6 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on main (b871a22) during the generation of this report, so 6ce787d was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩