ci: combine xcodebuild steps to fix github actions error

[synaptode]

This pull request combines the separate Build with xcodebuild and Test with xcodebuild steps in the iOS GitHub Actions workflow into a single Build and Test with xcodebuild step running xcodebuild clean build test. This resolves CI errors where running build and test separately can cause duplicate simulator booting issues or lost derived data.

---

PR created automatically by Jules for task 11205668165247948337 started by @synaptode

[google-labs-jules]

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

New to Jules? Learn more at jules.google/docs.

---

For security, I will only act on instructions from the user who triggered this task.