Add the ability for tasks to target the center pane (#22004)

Closes #20060
Closes #20720
Closes #19873
Closes #9445

Release Notes:

- Fixed a bug where tasks would be spawned with their working directory
set to a file in some cases
- Added the ability to spawn tasks in the center pane, when spawning
from a keybinding:

```json5
[
  {
    // Assuming you have a task labeled "echo hello"
    "ctrl--": [
      "task::Spawn",
      { "task_name": "echo hello", "target": "center" }
    ]
  }
]
```

crates/project/src/task_inventory.rs

@@ -177,7 +177,7 @@ impl Inventory {
                 let id_base = kind.to_id_base();
                 Some((
                     kind,
-                    task.resolve_task(&id_base, task_context)?,
+                    task.resolve_task(&id_base, Default::default(), task_context)?,
                     not_used_score,
                 ))
             })
@@ -397,7 +397,7 @@ mod test_inventory {
             let id_base = task_source_kind.to_id_base();
             inventory.task_scheduled(
                 task_source_kind.clone(),
-                task.resolve_task(&id_base, &TaskContext::default())
+                task.resolve_task(&id_base, Default::default(), &TaskContext::default())
                     .unwrap_or_else(|| panic!("Failed to resolve task with name {task_name}")),
             );
         });