tasks: Reorganize task modal (#11752)

![image](https://github.com/zed-industries/zed/assets/24362066/bc7cc3d3-d9fc-4be6-b9b6-e3d8edf5b533)

Release Notes:
- Improved tasks modal by highlighting a distinction between a task
template and concrete task instance and surfacing available keybindings
more prominently. Task templates are now always available in the modal,
even if there's already a history entry with the same label.
- Changed default key binding for "picker::UseSelectedQuery" to `opt-e`.

crates/task/src/task_template.rs

@@ -39,20 +39,6 @@ pub struct TaskTemplate {
     /// Whether to allow multiple instances of the same task to be run, or rather wait for the existing ones to finish.
     #[serde(default)]
     pub allow_concurrent_runs: bool,
-    // Tasks like "execute the selection" better have the constant labels (to avoid polluting the history with temporary tasks),
-    // and always use the latest context with the latest selection.
-    //
-    // Current impl will always pick previously spawned tasks on full label conflict in the tasks modal and terminal tabs, never
-    // getting the latest selection for them.
-    // This flag inverts the behavior, effectively removing all previously spawned tasks from history,
-    // if their full labels are the same as the labels of the newly resolved tasks.
-    // Such tasks are still re-runnable, and will use the old context in that case (unless the rerun task forces this).
-    //
-    // Current approach is relatively hacky, a better way is understand when the new resolved tasks needs a rerun,
-    // and replace the historic task accordingly.
-    #[doc(hidden)]
-    #[serde(default)]
-    pub ignore_previously_resolved: bool,
     /// What to do with the terminal pane and tab, after the command was started:
     /// * `always` — always show the terminal pane, add and focus the corresponding task's tab in it (default)
     /// * `never` — avoid changing current terminal pane focus, but still add/reuse the task's tab there