Add ability to use basic auth with programmatic server

[philippjfr]

Fixes #4906

[codecov]

Codecov Report

Merging #4926 (87dd542) into main (95bdcb2) will increase coverage by 0.00%.
The diff coverage is 73.68%.

@@           Coverage Diff           @@
##             main    #4926   +/-   ##
=======================================
  Coverage   83.43%   83.43%           
=======================================
  Files         270      270           
  Lines       38171    38187   +16     
=======================================
+ Hits        31849    31863   +14     
- Misses       6322     6324    +2     

Flag	Coverage Δ
ui-tests	40.88% <52.63%> (-0.01%)	⬇️
unitexamples-tests	73.38% <31.57%> (-0.01%)	⬇️

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Impacted Files	Coverage Δ
panel/io/server.py	76.83% <57.14%> (-0.26%)	⬇️
panel/auth.py	44.44% <77.77%> (+0.37%)	⬆️
panel/command/serve.py	40.92% <100.00%> (ø)
panel/config.py	77.04% <100.00%> (ø)
panel/io/state.py	73.39% <100.00%> (+0.37%)	⬆️

... and 3 files with indirect coverage changes

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