Fix: update token in blocking task

* attempt to fix https://github.com/hrkfdn/ncspot/issues/1358

mpris runs inside `tokio::runtime.spawn`. At some point it hits `metadata_changed->WebApi::track->api_with_retry`, which gets 401 response and tries to update the token.

This goes into `update_token`, which at a certain point calls *blocking* `token_rx.recv()`. Tokio runtime is not happy about that, as it uses the same thread for the `run_loop` in the worker. That's why `tokio::select!` doesn't work, we're essentially deadlocking, so the worker never pick up `RequestToken` command and `update_token` block forever.

Here I'm changing `update_token` to wrap `recv` in `spawn_blocking`, which makes `update_token` return a `JoinHandle`, on which the caller has to await. This doesn't work nicely in case of mpris though, as it is not an async function, and I don't know how to make it async as it goes through the dbus `metadata_changed` interface. My best effort here is to do `and_then`, which seems to work, but I'm not confident that's the right approach.

* fmt

* move token_rx.recv inside spawn_blocking

src/spotify.rs

@@ -83,7 +83,11 @@ impl Spotify {
         spotify.set_volume(volume);
 
         spotify.api.set_worker_channel(spotify.channel.clone());
-        spotify.api.update_token();
+        ASYNC_RUNTIME
+            .get()
+            .unwrap()
+            .block_on(spotify.api.update_token().unwrap())
+            .ok();
 
         spotify.api.set_user(user);