Fix nested popover closing PreviewTrigger on hover

[HamedFarazi]

Closes #10443

Summary

Fixes an issue where a nested Popover opened from inside a PreviewTrigger popover caused the parent PreviewTrigger popover to close when moving the pointer into the nested overlay.

The issue happened because the nested overlay is rendered outside of the PreviewTrigger popover boundary, causing the hover interaction to be interpreted as leaving the preview area.

This change adds regression coverage for nested overlays inside PreviewTrigger and ensures the parent preview remains open while interacting with child overlays.

✅ Pull Request Checklist:

• Included link to corresponding React Spectrum GitHub Issue.
• Added/updated unit tests and storybook for this change (for new code or code which already has tests).
• Filled out test instructions.
• Updated documentation (if it already exists for this component).
• Looked at the Accessibility Practices for this feature - ARIA Practices
• I understand every change in this PR and can explain why it's there.
• If AI-assisted, I followed our AI contribution guidance and pointed my assistant at https://github.com/adobe/react-spectrum/blob/main/CLAUDE.md.

📝 Test Instructions:

Automated tests

Run:

yarn jest packages/react-aria-components/test/PreviewTrigger.test.js

## 🧢 Your Project:
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