fix: copy attributes passed from the user to avoid mutation

[stibrew]

This PR fixes #4059

TODO:

• GitHub Actions have all passed
• Test coverage is 100% (Codecov passes)

[d-v-b]

Thank you!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.53%. Comparing base (3d8746a) to head (4b719a9).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4060   +/-   ##
=======================================
  Coverage   93.53%   93.53%           
=======================================
  Files          89       89           
  Lines       11901    11901           
=======================================
  Hits        11132    11132           
  Misses        769      769           

Files with missing lines	Coverage Δ
src/zarr/core/group.py	95.20% <100.00%> (ø)
src/zarr/core/metadata/common.py	100.00% <100.00%> (ø)

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[d-v-b]

@stibrew could you write up a release note for our changelog? see https://zarr.readthedocs.io/en/stable/contributing/#changelog

[stibrew]

@stibrew could you write up a release note for our changelog? see https://zarr.readthedocs.io/en/stable/contributing/#changelog

Done. Thank you as well!