Prevent unnecessary layout pass

[bryankeller]

Details

Instead of unconditionally marking the layout as dirty, we should just do it if the layout direction changed. This works around an expected behavior of SwiftUI, which might cause it to give new trait collections to views even if nothing has changed.

Related Issue

N/A

Motivation and Context

Internal Airbnb issue

How Has This Been Tested

Example project

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.