sidebar: Debounce `Sidebar::update_entries` (#57803)

Follow up on https://github.com/zed-industries/zed/pull/57717
Release Notes:

- N/A or Added/Fixed/Improved ...
f7dc726209Lukas Wirth committed on 6/5/2026, 4:57:00 PM· committed by GitHubparentbefa775
6 files changedLine totals unavailable