debugger: Fix the JavaScript debug terminal scenario (#33924)

There were a couple of things preventing this from working:

- our hack to stop the node REPL from appearing broke in recent versions
of the JS DAP that started passing `--experimental-network-inspection`
by default
- we had lost the ability to create a debug terminal without specifying
a program

This PR fixes those issues. We also fixed environment variables from the
**runInTerminal** request not getting passed to the spawned program.

Release Notes:

- Debugger: Fix RunInTerminal not working for JavaScript debugger.

---------

Co-authored-by: Cole Miller <cole@zed.dev>

crates/task/src/shell_builder.rs

@@ -149,17 +149,23 @@ impl ShellBuilder {
         }
     }
     /// Returns the program and arguments to run this task in a shell.
-    pub fn build(mut self, task_command: String, task_args: &Vec<String>) -> (String, Vec<String>) {
-        let combined_command = task_args
-            .into_iter()
-            .fold(task_command, |mut command, arg| {
-                command.push(' ');
-                command.push_str(&self.kind.to_shell_variable(arg));
-                command
-            });
+    pub fn build(
+        mut self,
+        task_command: Option<String>,
+        task_args: &Vec<String>,
+    ) -> (String, Vec<String>) {
+        if let Some(task_command) = task_command {
+            let combined_command = task_args
+                .into_iter()
+                .fold(task_command, |mut command, arg| {
+                    command.push(' ');
+                    command.push_str(&self.kind.to_shell_variable(arg));
+                    command
+                });
 
-        self.args
-            .extend(self.kind.args_for_shell(self.interactive, combined_command));
+            self.args
+                .extend(self.kind.args_for_shell(self.interactive, combined_command));
+        }
 
         (self.program, self.args)
     }