codify "platform" into resolution logic, server-fn/fullstack overhaul (#4596)

overhaul dioxus fullstack using a new implementation of server_fn

This PR is a complete rewrite of dioxus fullstack designed to improve compatibility with axum and to fix a number of compilation errors based on feature flag unification plumbing through macros.

examples/10-integrations/native-headless-in-bevy/src/main.rs

@@ -0,0 +1,29 @@
+mod bevy_scene_plugin;
+mod dioxus_in_bevy_plugin;
+mod ui;
+
+use crate::bevy_scene_plugin::BevyScenePlugin;
+use crate::dioxus_in_bevy_plugin::DioxusInBevyPlugin;
+use crate::ui::{ui, UIProps};
+use bevy::prelude::*;
+
+fn main() {
+    #[cfg(feature = "tracing")]
+    tracing_subscriber::fmt::init();
+
+    let (ui_sender, ui_receiver) = crossbeam_channel::unbounded();
+    let (app_sender, app_receiver) = crossbeam_channel::unbounded();
+    let props = UIProps {
+        ui_sender,
+        app_receiver,
+    };
+
+    App::new()
+        .add_plugins(DefaultPlugins)
+        .add_plugins(DioxusInBevyPlugin::<UIProps> { ui, props })
+        .add_plugins(BevyScenePlugin {
+            app_sender,
+            ui_receiver,
+        })
+        .run();
+}