feat: Added section support to Picker

[bmingles]

• Picker component now supports
  children
• Re-exported Spectrum Item + Section components

Supports deephaven/deephaven-plugins/issues/292

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 12 lines in your changes are missing coverage. Please review.

Project coverage is 46.07%. Comparing base (8892074) to head (d04b0cf).
Report is 2 commits behind head on main.

Files	Patch %	Lines
packages/components/src/spectrum/picker/Picker.tsx	0.00%	10 Missing ⚠️
...mponents/src/spectrum/picker/PickerItemContent.tsx	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1847      +/-   ##
==========================================
+ Coverage   46.03%   46.07%   +0.03%     
==========================================
  Files         635      635              
  Lines       37935    37978      +43     
  Branches     9563     9586      +23     
==========================================
+ Hits        17465    17499      +34     
- Misses      20416    20425       +9     
  Partials       54       54              

Flag	Coverage Δ
unit	46.07% <80.00%> (+0.03%)	⬆️

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