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/08-apis/scroll_to_top.rs

@@ -0,0 +1,38 @@
+//! Scroll elements using their MountedData
+//!
+//! Dioxus exposes a few helpful APIs around elements (mimicking the DOM APIs) to allow you to interact with elements
+//! across the renderers. This includes scrolling, reading dimensions, and more.
+//!
+//! In this example we demonstrate how to scroll to the top of the page using the `scroll_to` method on the `MountedData`
+
+use dioxus::prelude::*;
+
+fn main() {
+    dioxus::launch(app);
+}
+
+fn app() -> Element {
+    let mut header_element = use_signal(|| None);
+
+    rsx! {
+        div {
+            h1 {
+                onmounted: move |cx| header_element.set(Some(cx.data())),
+                "Scroll to top example"
+            }
+
+            for i in 0..100 {
+                div { "Item {i}" }
+            }
+
+            button {
+                onclick: move |_| async move {
+                    if let Some(header) = header_element.cloned() {
+                        header.scroll_to(ScrollBehavior::Smooth).await.unwrap();
+                    }
+                },
+                "Scroll to top"
+            }
+        }
+    }
+}