feat: Add CollapsibleSection

[FrederikBolding]

Add CollapsibleSection component, including structs, types etc.

https://consensyssoftware.atlassian.net/browse/WPC-959

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Note

Medium Risk
Adds a new JSX element and wires it into core UI validation/allowed-element unions, which could affect interface creation/validation behavior and error messaging across Snaps UIs.

Overview
Adds a new CollapsibleSection JSX component (with label, optional isLoading/isExpanded, and layout props) and exports it as a first-class Snaps UI element.

Updates JSX validation to recognize and validate CollapsibleSection (including adding it to root/box child unions), adds component/struct test coverage, and adjusts the snap_createInterface invalid-param test expectation to include the new allowed UI type.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.56%. Comparing base (c78b534) to head (a7097d3).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3952   +/-   ##
=======================================
  Coverage   98.56%   98.56%           
=======================================
  Files         427      428    +1     
  Lines       12344    12348    +4     
  Branches     1939     1939           
=======================================
+ Hits        12167    12171    +4     
  Misses        177      177           

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