[testing] Test Xcode 26 support with net9 and net10 workloads from macios

[rmarinho]

We need to test .NET MAUI with Xcode 26, specifically using the net9 and net10 workloads from macios.

Requirements:

• Use the correct macios packages and feeds for net9 and net10 workloads.
• Setup provisioning with Xcode 26 beta 4.
• Build and run with target framework net10-ios26.0.
• Document any issues or incompatibilities found during this process.

Checklist:

• Gather the correct package versions and feeds for net9/net10.
• Setup test machine with Xcode 26 beta 4 and provision the environment.
• Build and run sample apps with net10-ios26.0 target.
• Report on any required changes, workarounds, or blockers.

This is required to ensure MAUI workloads are ready for the next major iOS release.

[borrmann]

Can we already build and publish MAUI apps using .NET 9 with XCode 26?