relink: try to determine iscopy() from metadata if possible

[skshetry]

No description provided.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 90.90909% with 3 lines in your changes missing coverage. Please review.

Project coverage is 71.83%. Comparing base (eed0062) to head (a8b5ddf).

Files	Patch %	Lines
src/dvc_data/hashfile/checkout.py	50.00%	1 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #562      +/-   ##
==========================================
+ Coverage   70.58%   71.83%   +1.25%     
==========================================
  Files          67       67              
  Lines        4947     4975      +28     
  Branches      833      837       +4     
==========================================
+ Hits         3492     3574      +82     
+ Misses       1248     1201      -47     
+ Partials      207      200       -7     

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