wip: support icons inside of S2 DisclosureTitle

[yihuiliao]

Closes #9797

since there weren't any designs for this, i based the spacing between the icon + label off of S2 ListView. the rest of the spacing, like the padding between the edge + chevron or the chevron + label (or icon), i left the same as it was previously.

we should probably talk to design about this before we proceed but figured we could get more movement on it if we had something to present

✅ 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

📝 Test Instructions:

🧢 Your Project:

[rspbot]

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