Raise error if atlas affines don't match across participants

[tsalo]

Closes #1069. This is a temporary solution, until XCP-D starts using the NiPreps resampler tool to just resample preprocessing derivatives to a requested space and resolution (see #1076).

Changes proposed in this pull request

• Add a step in copy_atlas that checks if the new resampled NIfTI atlas's affine matches the existing one's. If it doesn't match, then XCP-D will raise a ValueError.
• Convert copy_atlas to an interface (CopyAtlas).

[codecov]

Codecov Report

Attention: Patch coverage is 96.29630% with 2 lines in your changes missing coverage. Please review.

Project coverage is 82.43%. Comparing base (f9a597d) to head (b483299).
Report is 113 commits behind head on main.

Files	Patch %	Lines
xcp_d/interfaces/bids.py	95.83%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1075      +/-   ##
==========================================
+ Coverage   82.33%   82.43%   +0.10%     
==========================================
  Files          48       48              
  Lines        5897     5916      +19     
  Branches      796      798       +2     
==========================================
+ Hits         4855     4877      +22     
+ Misses        839      837       -2     
+ Partials      203      202       -1     

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