feat: Cherry-pick DH-18779: Auto-resize column header groups

[vbabich]

Add missing change from #2540:

• Pass expandDescendants parameter to the model in IrisGrid.toggleExpandColumn

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 48.43%. Comparing base (736064d) to head (ccf1518).

Additional details and impacted files

@@               Coverage Diff               @@
##           release/v0.85    #2563    +/-   ##
===============================================
  Coverage          48.43%   48.43%            
===============================================
  Files                712      712            
  Lines              39734    39734            
  Branches            9921    10111   +190     
===============================================
  Hits               19244    19244            
+ Misses             20477    20433    -44     
- Partials              13       57    +44     

Flag	Coverage Δ
unit	48.43% <100.00%> (ø)

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