Stamping bugfix with group/chord header errback linking

[Nusnus]

When stamping a group that shares a link error, this causes all links to contain the same stamping.
This fix allows each errback to have its own stamps by using clone() when linking the errback signature.

This fix also takes into consideration Chords with the allow_error_cb_on_chord_header flag True.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (51b2846) 87.15% compared to head (dcc6dce) 87.15%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #8347   +/-   ##
=======================================
  Coverage   87.15%   87.15%           
=======================================
  Files         148      148           
  Lines       18467    18467           
  Branches     3148     3148           
=======================================
  Hits        16095    16095           
  Misses       2094     2094           
  Partials      278      278           

Flag	Coverage Δ
unittests	87.12% <100.00%> (ø)

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Impacted Files	Coverage Δ
celery/canvas.py	97.44% <100.00%> (ø)

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