Support State with #[derive(FromRequest[Parts])] (#1391)

* Support `State` with `#[derive(FromRequest[Parts])]`

Fixes https://github.com/tokio-rs/axum/issues/1314

This makes it possible to extract things via `State` in
`#[derive(FromRequet)]`:

```rust
struct Foo {
    state: State<AppState>,
}
```

The state can also be inferred in a lot of cases so you only need to
write:

```rust
struct Foo {
    // since we're using `State<AppState>` we know the state has to be
    // `AppState`
    state: State<AppState>,
}
```

Same for

```rust
struct Foo {
    #[from_request(via(State))]
    state: AppState,
}
```

And

```rust
struct AppState {}
```

I think I've covered all the edge cases but there are (unsurprisingly) a
few.

* make sure things can be combined with other extractors

* main functions in ui tests don't need to be async

* Add test for multiple identicaly state types

* Add failing test for multiple states

axum-macros/tests/from_request/pass/state_cookie.rs

@@ -0,0 +1,27 @@
+use axum_macros::FromRequest;
+use axum::extract::FromRef;
+use axum_extra::extract::cookie::{PrivateCookieJar, Key};
+
+#[derive(FromRequest)]
+#[from_request(state(AppState))]
+struct Extractor {
+    cookies: PrivateCookieJar,
+}
+
+struct AppState {
+    key: Key,
+}
+
+impl FromRef<AppState> for Key {
+    fn from_ref(input: &AppState) -> Self {
+        input.key.clone()
+    }
+}
+
+fn assert_from_request()
+where
+    Extractor: axum::extract::FromRequest<AppState, axum::body::Body, Rejection = axum::response::Response>,
+{
+}
+
+fn main() {}