Add execution and mime rendering utilities for pyodide

[philippjfr]

Useful for evaluating Panel code in a Pyodide context and then rendering the results.

[codecov]

Codecov Report

Merging #3851 (e2dcf15) into master (213bb21) will increase coverage by 0.13%.
The diff coverage is 90.38%.

@@            Coverage Diff             @@
##           master    #3851      +/-   ##
==========================================
+ Coverage   82.86%   82.99%   +0.13%     
==========================================
  Files         222      224       +2     
  Lines       32453    32565     +112     
==========================================
+ Hits        26891    27027     +136     
+ Misses       5562     5538      -24     

Flag	Coverage Δ
ui-tests	34.24% <35.89%> (+0.04%)	⬆️
unitexamples-tests	75.45% <90.38%> (+0.17%)	⬆️

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Impacted Files	Coverage Δ
panel/io/pyodide.py	0.00% <0.00%> (ø)
panel/io/mime_render.py	88.77% <88.77%> (ø)
panel/tests/io/test_mime_render.py	100.00% <100.00%> (ø)
panel/tests/command/test_serve.py	83.54% <0.00%> (-1.46%)	⬇️
panel/io/state.py	69.16% <0.00%> (-0.19%)	⬇️
panel/tests/util.py	89.21% <0.00%> (-0.11%)	⬇️
panel/io/jupyter_server_extension.py	0.00% <0.00%> (ø)
panel/tests/ui/widgets/test_tabulator.py	99.00% <0.00%> (+0.11%)	⬆️
panel/pane/idom.py	28.36% <0.00%> (+0.19%)	⬆️
panel/util.py	87.54% <0.00%> (+0.37%)	⬆️
... and 2 more

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