Fix safe area inset resolution across coordinate spaces

[Kyle-Ye]

Summary

• Convert safe-area boundaries into the local coordinate space before resolving insets.
• Fix corner-point rectangle construction for non-zero-based ArraySlice values.

Fixes #964.

[codecov]

Codecov Report

❌ Patch coverage is 8.77193% with 52 lines in your changes missing coverage. Please review.
✅ Project coverage is 15.14%. Comparing base (1ed914d) to head (b55310d).

Files with missing lines	Patch %	Lines
...ources/OpenSwiftUICore/Layout/SafeAreaInsets.swift	0.00%	52 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #965      +/-   ##
==========================================
+ Coverage   15.12%   15.14%   +0.01%     
==========================================
  Files         687      687              
  Lines       46487    46528      +41     
==========================================
+ Hits         7033     7046      +13     
- Misses      39454    39482      +28     

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