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.

packages/fullstack/.vscode/settings.json

@@ -0,0 +1,7 @@
+{
+    "rust-analyzer.cargo.features": "all",
+    "rust-analyzer.check.features": "all",
+    "rust-analyzer.cargo.extraArgs": [
+        "--tests"
+    ],
+}