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/03-assets-styling/custom_assets.rs

@@ -0,0 +1,22 @@
+//! A simple example on how to use assets loading from the filesystem.
+//!
+//! Dioxus provides the asset!() macro which is a convenient way to load assets from the filesystem.
+//! This ensures the asset makes it into the bundle through dependencies and is accessible in environments
+//! like web and android where assets are lazily loaded using platform-specific APIs.
+
+use dioxus::prelude::*;
+
+static ASSET_PATH: Asset = asset!("/examples/assets/logo.png");
+
+fn main() {
+    dioxus::launch(app);
+}
+
+fn app() -> Element {
+    rsx! {
+        div {
+            h1 { "This should show an image:" }
+            img { src: ASSET_PATH }
+        }
+    }
+}