feat(view): implement _CALayerView

[Kyle-Ye]

Summary

• Add _CALayerView with typed layer updates and a CALayer convenience initializer.
• Integrate layer content with the renderer and require main-thread updates.
• Add SDK documentation for the update callback and initializers.

[tuist]

🛠️ Tuist Run Report 🛠️

Tests 🧪

Scheme	Status	Ran test modules	Commit
OpenSwiftUI	✅	7	d5537379b

Builds 🔨

Scheme	Status	Duration	Commit
OpenSwiftUI	✅	1m 13s	d5537379b

[codecov]

Codecov Report

❌ Patch coverage is 0% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 32.78%. Comparing base (de48bff) to head (5592124).

Files with missing lines	Patch %	Lines
Sources/OpenSwiftUI/View/CALayerView.swift	0.00%	14 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1116      +/-   ##
==========================================
- Coverage   32.79%   32.78%   -0.02%     
==========================================
  Files         822      823       +1     
  Lines       66340    66354      +14     
==========================================
- Hits        21759    21755       -4     
- Misses      44581    44599      +18     

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