Add UnaryLayout and LayoutProxy

[Kyle-Ye]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 84 lines in your changes missing coverage. Please review.

Project coverage is 21.82%. Comparing base (73e1eb0) to head (074f31d).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
Sources/OpenSwiftUICore/Layout/LayoutProxy.swift	0.00%	71 Missing ⚠️
Sources/OpenSwiftUICore/Layout/UnaryLayout.swift	0.00%	8 Missing ⚠️
...wiftUICore/Layout/Stack/LayoutPriorityLayout.swift	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #299      +/-   ##
==========================================
- Coverage   21.93%   21.82%   -0.12%     
==========================================
  Files         348      350       +2     
  Lines       16591    16674      +83     
==========================================
- Hits         3640     3639       -1     
- Misses      12951    13035      +84     

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