linux: Save opened workspace when closing last window (#15754)

Fixes https://github.com/zed-industries/zed/issues/15642
(also fixes a bug where replacing a workspace in the same window would
reopen the old project after closing with `CTRL + Q`)

Release Notes:

- Linux: Fixed last workspace not being restored on startup
([#15642](https://github.com/zed-industries/zed/issues/15642)).
- Fixed a bug where a closed workspace could be reopened on startup.

crates/collab/src/tests/editor_tests.rs

@@ -43,7 +43,7 @@ use std::{
     },
 };
 use text::Point;
-use workspace::Workspace;
+use workspace::{CloseIntent, Workspace};
 
 #[gpui::test(iterations = 10)]
 async fn test_host_disconnect(
@@ -134,7 +134,9 @@ async fn test_host_disconnect(
 
     // Ensure client B is not prompted to save edits when closing window after disconnecting.
     let can_close = workspace_b
-        .update(cx_b, |workspace, cx| workspace.prepare_to_close(true, cx))
+        .update(cx_b, |workspace, cx| {
+            workspace.prepare_to_close(CloseIntent::Quit, cx)
+        })
         .unwrap()
         .await
         .unwrap();