## Summary

Add a chevron (`Disclosure`) to each file group header in Text Finder,
letting you fold/unfold that file's matches. Fold state is cleared
whenever a new search starts.

## Test plan

- [x] Open Text Finder, run a search with matches in multiple files
- [x] Click a header's chevron, confirm its matches hide/show and
selection lands on a visible row
- [x] Start a new search, confirm folded state doesn't carry over

Release Notes:

- Added the ability to collapse per-file match groups in Text Finder

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Co-authored-by: ozacod <ozacod@users.noreply.github.com>
Co-authored-by: Danilo Leal <daniloleal09@gmail.com>