Clean up orphaned hotkeys when extension is uninstalled (#45452)

When an extension with assigned hotkeys was uninstalled, its hotkey
bindings remained in settings.json and continued to be registered,
consuming the key combination globally without any effect.

Now when an extension is removed, any hotkeys belonging to its commands
are also removed from settings and persisted, so the hotkeys are freed
on the next settings reload.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>