debugger: Add debug task picker to new session modal (#29702)

## Preview 

![image](https://github.com/user-attachments/assets/203a577f-3b38-4017-9571-de1234415162)


### TODO
- [x] Add scenario picker to new session modal
- [x] Make debugger start action open new session modal instead of task
modal
- [x] Fix `esc` not clearing the cancelling the new session modal while
it's in scenario or attach mode
- [x] Resolve debug scenario's correctly

Release Notes:

- N/A

crates/task/src/lib.rs

@@ -19,7 +19,8 @@ pub use debug_format::{
     AttachRequest, DebugRequest, DebugScenario, DebugTaskFile, LaunchRequest, TcpArgumentsTemplate,
 };
 pub use task_template::{
-    DebugArgsRequest, HideStrategy, RevealStrategy, TaskModal, TaskTemplate, TaskTemplates,
+    DebugArgsRequest, HideStrategy, RevealStrategy, TaskTemplate, TaskTemplates,
+    substitute_all_template_variables_in_str,
 };
 pub use vscode_debug_format::VsCodeDebugTaskFile;
 pub use vscode_format::VsCodeTaskFile;
@@ -266,6 +267,10 @@ impl TaskVariables {
             }
         })
     }
+
+    pub fn iter(&self) -> impl Iterator<Item = (&VariableName, &String)> {
+        self.0.iter()
+    }
 }
 
 impl FromIterator<(VariableName, String)> for TaskVariables {

crates/task/src/task_template.rs

@@ -83,15 +83,6 @@ pub enum DebugArgsRequest {
     Attach(AttachRequest),
 }
 
-#[derive(Clone, Debug, PartialEq, Eq)]
-/// The type of task modal to spawn
-pub enum TaskModal {
-    /// Show regular tasks
-    ScriptModal,
-    /// Show debug tasks
-    DebugModal,
-}
-
 /// What to do with the terminal pane and tab, after the command was started.
 #[derive(Default, Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize, JsonSchema)]
 #[serde(rename_all = "snake_case")]
@@ -302,7 +293,7 @@ fn to_hex_hash(object: impl Serialize) -> anyhow::Result<String> {
     Ok(hex::encode(hasher.finalize()))
 }
 
-fn substitute_all_template_variables_in_str<A: AsRef<str>>(
+pub fn substitute_all_template_variables_in_str<A: AsRef<str>>(
     template_str: &str,
     task_variables: &HashMap<String, A>,
     variable_names: &HashMap<String, VariableName>,