Move middleware::from_fn into axum (#719)

* Move `middleware::from_fn` into axum

* changelog

* fix feature

* Rephrase changelog a bit

examples/print-request-response/src/main.rs

@@ -7,11 +7,11 @@
 use axum::{
     body::{Body, Bytes},
     http::{Request, StatusCode},
+    middleware::{self, Next},
     response::{IntoResponse, Response},
     routing::post,
     Router,
 };
-use axum_extra::middleware::{self, Next};
 use std::net::SocketAddr;
 
 #[tokio::main]

examples/prometheus-metrics/src/main.rs

@@ -7,8 +7,14 @@
 //! cargo run -p example-prometheus-metrics
 //! ```
 
-use axum::{extract::MatchedPath, http::Request, response::IntoResponse, routing::get, Router};
-use axum_extra::middleware::{self, Next};
+use axum::{
+    extract::MatchedPath,
+    http::Request,
+    middleware::{self, Next},
+    response::IntoResponse,
+    routing::get,
+    Router,
+};
 use metrics_exporter_prometheus::{Matcher, PrometheusBuilder, PrometheusHandle};
 use std::{
     future::ready,