Add ChatBox methods and replacing ChatRow values

[ahuang11]

As I was building my AI chat box I felt like pn.widgets.ChatBox was missing some core functionality so this PR adds:

• Allows updating row message
• Adds insert, pop, replace list methods

[ahuang11]

Actually dropping support for Allows updating row message because it gets out of sync with ChatBox.

[codecov]

Codecov Report

Merging #5118 (e931bb4) into main (111242a) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #5118      +/-   ##
==========================================
+ Coverage   83.71%   83.75%   +0.03%     
==========================================
  Files         274      274              
  Lines       39274    39391     +117     
==========================================
+ Hits        32880    32993     +113     
- Misses       6394     6398       +4     

Flag	Coverage Δ
ui-tests	40.45% <11.76%> (+0.02%)	⬆️
unitexamples-tests	73.80% <100.00%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
panel/tests/widgets/test_chatbox.py	100.00% <100.00%> (ø)
panel/widgets/chatbox.py	95.54% <100.00%> (+0.20%)	⬆️

... and 10 files with indirect coverage changes

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[ahuang11]

https://discourse.holoviz.org/t/openai-conversation-using-chatbox/5548/3?u=ahuang11

[philippjfr]

Looking great!