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/languages/src/python.rs

@@ -187,7 +187,6 @@ pub(super) fn python_task_context() -> ContextProviderWithTasks {
             label: "execute selection".to_owned(),
             command: "python3".to_owned(),
             args: vec!["-c".to_owned(), VariableName::SelectedText.template_value()],
-            ignore_previously_resolved: true,
             ..TaskTemplate::default()
         },
         TaskTemplate {