Always store state in an Arc (#1270)

* Add extension and state benchmarks

* wip

* Arc the state everywhere

* don't require `S: Clone`

* fix example

axum-extra/src/routing/mod.rs

@@ -178,7 +178,7 @@ pub trait RouterExt<S, B>: sealed::Sealed {
 impl<S, B> RouterExt<S, B> for Router<S, B>
 where
     B: axum::body::HttpBody + Send + 'static,
-    S: Clone + Send + Sync + 'static,
+    S: Send + Sync + 'static,
 {
     #[cfg(feature = "typed-routing")]
     fn typed_get<H, T, P>(self, handler: H) -> Self

axum-extra/src/routing/resource.rs

@@ -53,7 +53,7 @@ where
 impl<S, B> Resource<S, B>
 where
     B: axum::body::HttpBody + Send + 'static,
-    S: Clone + Send + Sync + 'static,
+    S: Send + Sync + 'static,
 {
     /// Create a `Resource` with the given name and state.
     ///