feat: DH-13515: Expandable columns support

[vbabich]

• Add new ExpandableColumnGridModel interface for models with expandable columns
• Export ColumnHeaderGroup and IrisGridCellRendererUtils from @deephaven/iris-grid
• Add IrisGrid methods to expand/collapse columns
• Update metrics on columns change in IrisGrid
• IrisGridMetricCalculator now stores user column widths by name
• parseColumnHeaderGroups in IrisGridUtils has an optional argument allowing to preserve the correct header group class
• IrisGrid context menu shows Expand All and Collapse All if supported in the model
• Update e2e snapshots, add unit tests

[codecov]

Codecov Report

❌ Patch coverage is 71.55963% with 31 lines in your changes missing coverage. Please review.
✅ Project coverage is 44.94%. Comparing base (ee2ba42) to head (026d442).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
packages/iris-grid/src/IrisGrid.tsx	62.16%	14 Missing ⚠️
packages/iris-grid/src/IrisGridMetricCalculator.ts	74.50%	13 Missing ⚠️
...d/src/mousehandlers/IrisGridContextMenuHandler.tsx	50.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2537      +/-   ##
==========================================
+ Coverage   44.56%   44.94%   +0.38%     
==========================================
  Files         764      765       +1     
  Lines       42821    42915      +94     
  Branches    10971    10793     -178     
==========================================
+ Hits        19084    19290     +206     
+ Misses      23726    23612     -114     
- Partials       11       13       +2     

Flag	Coverage Δ
unit	44.94% <71.55%> (+0.38%)	⬆️

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[mofojed]

Looking good overall. A few small things/suggestions.