WIP Add Card UI tests

[thuydotm]

Addresses #3653 following the procedure in #3633. The newly added tests verify if Card components match the parameter setting values at initialization.

[philippjfr]

Thanks @thuydotm! Could you install pre-commit and then run pre-commit install? That way it will automatically apply our code style and linters. I'd also run pre-commit run -a the first time to fix up this PR.

[codecov]

Codecov Report

Merging #3654 (fa00f99) into master (f4cf0ff) will decrease coverage by 0.41%.
The diff coverage is 16.15%.

@@            Coverage Diff             @@
##           master    #3654      +/-   ##
==========================================
- Coverage   82.32%   81.90%   -0.42%     
==========================================
  Files         205      206       +1     
  Lines       27893    28064     +171     
==========================================
+ Hits        22963    22987      +24     
- Misses       4930     5077     +147     

Impacted Files	Coverage Δ
panel/tests/ui/widgets/test_card.py	16.15% <16.15%> (ø)
panel/io/callbacks.py	74.61% <0.00%> (-3.08%)	⬇️
panel/auth.py	39.34% <0.00%> (-2.11%)	⬇️
panel/util.py	85.60% <0.00%> (-0.38%)	⬇️

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[philippjfr]

Looks great, thank you!