Fix ChatBox issues

[ahuang11]

While trying to use it for an actual use case, I found some problems with it, namely:

1. Send button height stretches too far ChatBox Send button stretches too far. #5100
2. ChatBox inputs cannot be disabled ChatBox cannot be disabled #5099
3. pn.bind didn't work with append because previously, append doesn't actually trigger value in the latest patch
4. If append now trigger values, it does a whole refresh and liked again gets lost so I added logic to match up the messages along with index

[codecov]

Codecov Report

Merging #5101 (9c9f812) into main (285db25) will increase coverage by 0.79%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #5101      +/-   ##
==========================================
+ Coverage   82.93%   83.73%   +0.79%     
==========================================
  Files         274      274              
  Lines       39133    39254     +121     
==========================================
+ Hits        32455    32869     +414     
+ Misses       6678     6385     -293     

Flag	Coverage Δ
ui-tests	40.44% <16.94%> (-0.06%)	⬇️
unitexamples-tests	73.81% <100.00%> (+1.24%)	⬆️

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Impacted Files	Coverage Δ
panel/tests/widgets/test_chatbox.py	100.00% <100.00%> (ø)
panel/widgets/chatbox.py	95.33% <100.00%> (+0.10%)	⬆️

... and 18 files with indirect coverage changes

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[philippjfr]

Thanks for the fixes!