workspace: Fix last removed folder from workspace used to reopen on Zed startup (#34925)

Closes #34924

Now, when `local_paths` are empty, we detach `session_id` from that
workspace serialization item. This way, when we restore it using the
default "last_session", we don't restore this workspace back. This is
same as when we use `cmd-w` to close window, which also sets
`session_id` to `None` before serialization.

Release Notes:

- Fixed an issue where last removed folder from workspace used to reopen
on Zed startup.

crates/workspace/src/persistence.rs

@@ -1336,6 +1336,14 @@ impl WorkspaceDb {
         }
     }
 
+    query! {
+        pub(crate) async fn set_session_id(workspace_id: WorkspaceId, session_id: Option<String>) -> Result<()> {
+            UPDATE workspaces
+            SET session_id = ?2
+            WHERE workspace_id = ?1
+        }
+    }
+
     pub async fn toolchain(
         &self,
         workspace_id: WorkspaceId,