[sorinc03]

When stretch sizing derives a child's main dimension from its aspect ratio, the computed border-box dimension is passed into an available-size parameter that includes margins. The child then subtracts main-axis margins again.

Include the main-axis margins in the two stretch/aspect-ratio assignments, matching the adjacent non-stretch aspect-ratio calculations. For the reported 400-wide root with 24-point margins and a 16:9 child, the child now measures 352×198 instead of 267×150.

Fixes #1788. This changes only the margin-box arithmetic in these branches, without changing Yoga's broader aspect-ratio semantics.

Test plan

• Added 10 independently Chrome-derived fixtures covering row/column, reverse directions, RTL, asymmetric/percentage margins, padding/border, relative positioning and a zero-main-margin control.
• Unmodified main fails 9 of the 10 final cases; fixed code passes all 10.
• Full C++ Debug and Release suites: 896/896 pass in each.
• Format check, lint, generated-source validation, JavaScript typecheck and complete fixture regeneration pass.
• Local AppleClang 21 requires the same existing GoogleTest warning downgrade (-Wno-error=character-conversion); no build-system workaround is included.
• Java/JavaScript runtime suites and public CI remain unrun locally.

Changelog:
[General][Fixed] - Preserve main-axis margins when stretching items with an aspect ratio