Improve CodeEditor warning dialog

[davidfig]

• fix bug with escape key not trigger CodeEditor save warning
• add warning dialog when changing code cell to a different cell
  • double click
  • = from outside cell
  • = within CellInput
• add escape anywhere in app to close code editor

The testing matrix is rather large:

Possible states

1. Code Editor is open or closed
2. Code Editor has changes or not
3. Code Editor has focus or not

Triggers

• Pressing escape (with states 2 and 3)
• Pressing the close button on code editor (with states 2 and 3)
• Double-clicking a code cell (with state 2)
• Pressing equals or slash on a code cell (with state 2)
• Pressing equals or slash on a non-code cell (with state 2)
• Typing = as the first character while cell input is open (with state 2)

Save Dialog choice
Need to check all the triggers against the three results of the dialog: Save and Run, Discard, and Cancel.

• Save and Run should save and run the cell and update it before performing the trigger
• Cancel should revert the original code cell's contents before performing the trigger
• Cancel should always leave the code cell the way it was with the unsaved change and cancel the triggering event

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Name	Status	Preview	Updated (UTC)
quadratic	✅ Ready (Inspect)	Visit Preview	Jan 8, 2024 4:45pm

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (f33d092) 88.52% compared to head (ce9e9a5) 88.52%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #967      +/-   ##
==========================================
- Coverage   88.52%   88.52%   -0.01%     
==========================================
  Files          99       99              
  Lines       17698    17764      +66     
==========================================
+ Hits        15668    15725      +57     
- Misses       2030     2039       +9     

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