Improve SwiftUI sizing

[bryankeller]

Details

Improve SwiftUI sizing. Rather than returning .infinity from the sizing functions when the proposed size is (nil, nil), we return a reasonable minimum size instead. This fixes an issue that causes a vertical CalendarViewRepresentable to freeze the app when displayed in a VStack / LazyVStack

Related Issue

N/A

Motivation and Context

Crash fix, also prevents some warning logs about infinite dimensions.

How Has This Been Tested

Example app

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.