Fix outdir not work when run dx bundle --platform web --outdir mydir (#3572)

* Make legacy asset dir optional
* properly implement outdir

---------

Co-authored-by: Jonathan Kelley <jkelleyrtp@gmail.com>
Co-authored-by:  Nathy-bajo <bajon7680@gmail.com>

packages/cli/src/config/dioxus_config.rs

@@ -22,8 +22,9 @@ impl Default for DioxusConfig {
     fn default() -> Self {
         Self {
             application: ApplicationConfig {
-                asset_dir: asset_dir_default(),
+                asset_dir: None,
                 sub_package: None,
+                out_dir: None,
             },
             web: WebConfig {
                 app: WebAppConfig {