Support local devcontainer features (#55225)

Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Closes #53486

Note that this builds off of #55117 because both touched similar code
areas; I thought it best to in order to avoid conflicts.

Release Notes:

- Added support for local features in dev containers
707c00b474KyleBarton committed on 5/26/2026, 7:13:00 AM· committed by GitHubparent3e77442
6 files changedLine totals unavailable