Update/Fix CI workflow

- Fixed cargo fmt
- Updated MSRV to v1.57.0, which is needed for `base64` v0.20
- Updated all actions to the latest versions. (Solves Annotation warnings)
- Replaced actions-rs with dtolnay actions or simple run's.
  actions-rs is not supported anymore, and also causes warnings.
- Use Ubuntu 20.04 for `linux / nightly`.
  The reason is that Ubuntu 22.04 uses OpenSSL v3, this currently is not compatible with hyper-tls it looks like. I also tried to update the `openssl-sys` crate but that doesn't solve the compile issue. Using a Ubuntu version that still has OpenSSL v1.1.1 resolves the CI for now.

src/async_impl/request.rs

@@ -253,7 +253,8 @@ impl RequestBuilder {
     {
         let mut header_value = b"Basic ".to_vec();
         {
-            let mut encoder = Base64Encoder::from(&mut header_value, &base64::engine::DEFAULT_ENGINE);
+            let mut encoder =
+                Base64Encoder::from(&mut header_value, &base64::engine::DEFAULT_ENGINE);
             // The unwraps here are fine because Vec::write* is infallible.
             write!(encoder, "{}:", username).unwrap();
             if let Some(password) = password {