Move `with_auth` method for `ClientConfig` into each component's features

[yoshidan]

Added google-cloud-default's WithAuthExt as a feature of each component.(features=["auth"])

How to migrate

• Remove google-cloud-default . Since auth is also the default feature, features=["auth"] is required only when the default feature is disabled, such as when using rustls-tls.

  google-cloud-storage = { version="xxx", default-features=false, features=["rustls-tls","auth"]}
  google-cloud-bigquery = { version="xxx", default-features=false, features=["rustls-tls","auth"]}

• Remove google_cloud_default from code. interface is not changed.

  
  use google_cloud_pubsub::client::{ClientConfig, Client};
  // use google_cloud_default::WithAuthExt;  <- remove dependency

async fn run() { let config = ClientConfig::default().with_auth().await.unwrap(); let client = Client::new(config).await.unwrap(); }