debugger: Mark DebugAdapterBinary::program as optional (#32534)

This allows us to support debugging with a debug adapter not managed by
Zed. Note that this is not a user facing change, as DebugAdapterBinary
is used to determine how to spawn a debugger. Thus, this should not
break any configs or anything like that.

Closes #ISSUE

Release Notes:

- N/A

crates/dap_adapters/src/javascript.rs

@@ -69,12 +69,14 @@ impl JsDebugAdapter {
         let (host, port, timeout) = crate::configure_tcp_connection(tcp_connection).await?;
 
         Ok(DebugAdapterBinary {
-            command: delegate
-                .node_runtime()
-                .binary_path()
-                .await?
-                .to_string_lossy()
-                .into_owned(),
+            command: Some(
+                delegate
+                    .node_runtime()
+                    .binary_path()
+                    .await?
+                    .to_string_lossy()
+                    .into_owned(),
+            ),
             arguments: vec![
                 adapter_path
                     .join(Self::ADAPTER_PATH)