Fix tasks not being stopped on reruns (#29786)

Follow-up of https://github.com/zed-industries/zed/pull/28993

* Tone down tasks' cancellation logging
* Fix task terminals' leak, disallowing to fully cancel the task by
dropping the terminal off the pane:

f619d5f02a/crates/terminal_view/src/terminal_panel.rs (L1464-L1471)

Release Notes:

- Fixed tasks not being stopped on reruns

crates/vim/src/command.rs

@@ -1466,9 +1466,22 @@ impl ShellExec {
                     show_command: false,
                     show_rerun: false,
                 };
-                workspace
-                    .spawn_in_terminal(spawn_in_terminal, window, cx)
-                    .detach_and_log_err(cx);
+
+                let task_status = workspace.spawn_in_terminal(spawn_in_terminal, window, cx);
+                cx.background_spawn(async move {
+                    match task_status.await {
+                        Some(Ok(status)) => {
+                            if status.success() {
+                                log::debug!("Vim shell exec succeeded");
+                            } else {
+                                log::debug!("Vim shell exec failed, code: {:?}", status.code());
+                            }
+                        }
+                        Some(Err(e)) => log::error!("Vim shell exec failed: {e}"),
+                        None => log::debug!("Vim shell exec got cancelled"),
+                    }
+                })
+                .detach();
             });
             return;
         };