Refactor handling of component stylesheets

[philippjfr]

Follow up to #6563 which avoids adding full stylesheets as link tags.

[codecov]

Codecov Report

Attention: Patch coverage is 17.85714% with 23 lines in your changes are missing coverage. Please review.

Project coverage is 22.20%. Comparing base (a396599) to head (67ea85c).
Report is 2 commits behind head on main.

Files	Patch %	Lines
panel/io/resources.py	7.69%	12 Missing ⚠️
panel/template/base.py	10.00%	9 Missing ⚠️
panel/template/golden/__init__.py	50.00%	1 Missing ⚠️
panel/theme/base.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #6571       +/-   ##
===========================================
- Coverage   82.98%   22.20%   -60.78%     
===========================================
  Files         313      313               
  Lines       46023    46032        +9     
===========================================
- Hits        38191    10222    -27969     
- Misses       7832    35810    +27978     

Flag	Coverage Δ
ui-tests	?
unitexamples-tests	22.20% <17.85%> (-49.04%)	⬇️

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