Ensure hash_funcs are applied recursively in cache

[philippjfr]

Fixes #4139

[codecov]

Codecov Report

Merging #4334 (0e01280) into main (47f231b) will decrease coverage by 0.15%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #4334      +/-   ##
==========================================
- Coverage   82.75%   82.61%   -0.15%     
==========================================
  Files         240      240              
  Lines       34558    34566       +8     
==========================================
- Hits        28598    28555      -43     
- Misses       5960     6011      +51     

Flag	Coverage Δ
ui-tests	37.99% <30.00%> (-0.31%)	⬇️
unitexamples-tests	73.79% <100.00%> (+<0.01%)	⬆️

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Impacted Files	Coverage Δ
panel/io/cache.py	83.69% <100.00%> (+1.02%)	⬆️
panel/tests/ui/widgets/test_misc.py	33.33% <0.00%> (-64.11%)	⬇️
panel/tests/ui/io/test_jupyter_server_extension.py	50.00% <0.00%> (-50.00%)	⬇️
panel/tests/ui/io/test_jupyterlite.py	89.74% <0.00%> (-7.70%)	⬇️
panel/tests/util.py	87.37% <0.00%> (-3.89%)	⬇️
panel/tests/ui/io/test_convert.py	93.10% <0.00%> (-2.59%)	⬇️
panel/tests/conftest.py	88.08% <0.00%> (-1.28%)	⬇️

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