Fix visionOS SwiftUI bar interaction

[bryankeller]

Change summary

This works around a visionOS bug that causes SwiftUI views contained in hosting controllers to have broken interaction if their zPosition's magnitude is too large. A safe workaround is to ensure that zPosition is always between -1 and 1, which provides ample precision for all of our needs.

How was it tested?

How did you verify that this change accomplished what you expected? Add more detail as needed.

• Wrote automated tests
• Built and ran on the iOS simulator
• Built and ran on a device

Pull request checklist

All items in this checklist must be completed before a pull request will be reviewed.

• Risky changes have been put behind a feature flag, e.g. CollectionViewConfiguration
• Added a CHANGELOG.md entry in the "Unreleased" section for any library changes