Fix printing of supplemental attributes

[daniel-thom]

The default Base.show method was printing circular references to objects internal to supplemental attributes. This solution uses the same method as is used for components.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.28%. Comparing base (0816ef2) to head (16f3306).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #395   +/-   ##
=======================================
  Coverage   78.28%   78.28%           
=======================================
  Files          71       71           
  Lines        5484     5484           
=======================================
  Hits         4293     4293           
  Misses       1191     1191           

Flag	Coverage Δ
unittests	78.28% <100.00%> (ø)

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Files with missing lines	Coverage Δ
src/utils/print.jl	74.68% <100.00%> (ø)