chore(proxy): remove postgres config parser and md5 support (#9990)

Keeping the `mock` postgres cplane adaptor using "stock" tokio-postgres
allows us to remove a lot of dead weight from our actual postgres
connection logic.

proxy/src/auth/backend/classic.rs

@@ -66,7 +66,7 @@ pub(super) async fn authenticate(
 
     Ok(ComputeCredentials {
         info: creds,
-        keys: ComputeCredentialKeys::AuthKeys(tokio_postgres::config::AuthKeys::ScramSha256(
+        keys: ComputeCredentialKeys::AuthKeys(postgres_client::config::AuthKeys::ScramSha256(
             scram_keys,
         )),
     })

proxy/src/auth/backend/console_redirect.rs

@@ -1,8 +1,8 @@
 use async_trait::async_trait;
+use postgres_client::config::SslMode;
 use pq_proto::BeMessage as Be;
 use thiserror::Error;
 use tokio::io::{AsyncRead, AsyncWrite};
-use tokio_postgres::config::SslMode;
 use tracing::{info, info_span};
 
 use super::ComputeCredentialKeys;

proxy/src/auth/backend/mod.rs

@@ -11,8 +11,8 @@ pub use console_redirect::ConsoleRedirectBackend;
 pub(crate) use console_redirect::ConsoleRedirectError;
 use ipnet::{Ipv4Net, Ipv6Net};
 use local::LocalBackend;
+use postgres_client::config::AuthKeys;
 use tokio::io::{AsyncRead, AsyncWrite};
-use tokio_postgres::config::AuthKeys;
 use tracing::{debug, info, warn};
 
 use crate::auth::credentials::check_peer_addr_is_in_list;

proxy/src/auth/flow.rs

@@ -227,7 +227,7 @@ pub(crate) async fn validate_password_and_exchange(
             };
 
             Ok(sasl::Outcome::Success(ComputeCredentialKeys::AuthKeys(
-                tokio_postgres::config::AuthKeys::ScramSha256(keys),
+                postgres_client::config::AuthKeys::ScramSha256(keys),
             )))
         }
     }