debugger: Fix issues with launch.json handling (#32563)

After this PR we can run all the in-tree launch.json examples from [this
repo](https://github.com/microsoft/vscode-recipes).

Things done:

- Fill in default cwd at a lower level for all adapters
- Update launch.json parsing for DebugScenario changes
- Imitate how VS Code normalizes the `type` field for JS debug tasks
- Make version field optional
- Extend the variable replacer a bit

Release Notes:

- Debugger Beta: fixed issues preventing loading and running of debug
tasks from VS Code's launch.json.

---------

Co-authored-by: Anthony Eid <hello@anthonyeid.me>
Co-authored-by: Anthony <anthony@zed.dev>
Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

crates/dap_adapters/src/codelldb.rs

@@ -21,18 +21,21 @@ impl CodeLldbDebugAdapter {
 
     fn request_args(
         &self,
+        delegate: &Arc<dyn DapDelegate>,
         task_definition: &DebugTaskDefinition,
     ) -> Result<dap::StartDebuggingRequestArguments> {
         // CodeLLDB uses `name` for a terminal label.
         let mut configuration = task_definition.config.clone();
 
-        configuration
+        let obj = configuration
             .as_object_mut()
-            .context("CodeLLDB is not a valid json object")?
-            .insert(
-                "name".into(),
-                Value::String(String::from(task_definition.label.as_ref())),
-            );
+            .context("CodeLLDB is not a valid json object")?;
+
+        obj.entry("name")
+            .or_insert(Value::String(String::from(task_definition.label.as_ref())));
+
+        obj.entry("cwd")
+            .or_insert(delegate.worktree_root_path().to_string_lossy().into());
 
         let request = self.request_kind(&configuration)?;
 
@@ -365,7 +368,7 @@ impl DebugAdapter for CodeLldbDebugAdapter {
                 "--settings".into(),
                 json!({"sourceLanguages": ["cpp", "rust"]}).to_string(),
             ],
-            request_args: self.request_args(&config)?,
+            request_args: self.request_args(delegate, &config)?,
             envs: HashMap::default(),
             connection: None,
         })