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/05-using-async/clock.rs

@@ -0,0 +1,42 @@
+//! A simple little clock that updates the time every few milliseconds.
+
+use async_std::task::sleep;
+use dioxus::prelude::*;
+use web_time::Instant;
+
+fn main() {
+    dioxus::launch(app);
+}
+
+fn app() -> Element {
+    let mut millis = use_signal(|| 0);
+
+    use_future(move || async move {
+        // Save our initial time
+        let start = Instant::now();
+
+        loop {
+            sleep(std::time::Duration::from_millis(27)).await;
+
+            // Update the time, using a more precise approach of getting the duration since we started the timer
+            millis.set(start.elapsed().as_millis() as i64);
+        }
+    });
+
+    // Format the time as a string
+    // This is rather cheap so it's fine to leave it in the render function
+    let time = format!(
+        "{:02}:{:02}:{:03}",
+        millis() / 1000 / 60 % 60,
+        millis() / 1000 % 60,
+        millis() % 1000
+    );
+
+    rsx! {
+        document::Stylesheet { href: asset!("/examples/assets/clock.css") }
+        div { id: "app",
+            div { id: "title", "Carpe diem 🎉" }
+            div { id: "clock-display", "{time}" }
+        }
+    }
+}