chore(proxy): vendor a subset of rust-postgres (#9930)

Our rust-postgres fork is getting messy. Mostly because proxy wants more
control over the raw protocol than tokio-postgres provides. As such,
it's diverging more and more. Storage and compute also make use of
rust-postgres, but in more normal usage, thus they don't need our crazy
changes.

Idea: 
* proxy maintains their subset
* other teams use a minimal patch set against upstream rust-postgres

Reviewing this code will be difficult. To implement it, I
1. Copied tokio-postgres, postgres-protocol and postgres-types from
00940fcdb5
2. Updated their package names with the `2` suffix to make them compile
in the workspace.
3. Updated proxy to use those packages
4. Copied in the code from tokio-postgres-rustls 0.13 (with some patches
applied https://github.com/jbg/tokio-postgres-rustls/pull/32
https://github.com/jbg/tokio-postgres-rustls/pull/33)
5. Removed as much dead code as I could find in the vendored libraries
6. Updated the tokio-postgres-rustls code to use our existing channel
binding implementation

proxy/src/compute.rs

@@ -13,7 +13,6 @@ use rustls::pki_types::InvalidDnsNameError;
 use thiserror::Error;
 use tokio::net::TcpStream;
 use tokio_postgres::tls::MakeTlsConnect;
-use tokio_postgres_rustls::MakeRustlsConnect;
 use tracing::{debug, error, info, warn};
 
 use crate::auth::parse_endpoint_param;
@@ -24,6 +23,7 @@ use crate::control_plane::errors::WakeComputeError;
 use crate::control_plane::messages::MetricsAuxInfo;
 use crate::error::{ReportableError, UserFacingError};
 use crate::metrics::{Metrics, NumDbConnectionsGuard};
+use crate::postgres_rustls::MakeRustlsConnect;
 use crate::proxy::neon_option;
 use crate::types::Host;
 
@@ -244,7 +244,6 @@ impl ConnCfg {
             let port = ports.get(i).or_else(|| ports.first()).unwrap_or(&5432);
             let host = match host {
                 Host::Tcp(host) => host.as_str(),
-                Host::Unix(_) => continue, // unix sockets are not welcome here
             };
 
             match connect_once(host, *port).await {
@@ -315,7 +314,7 @@ impl ConnCfg {
         };
         let client_config = client_config.with_no_client_auth();
 
-        let mut mk_tls = tokio_postgres_rustls::MakeRustlsConnect::new(client_config);
+        let mut mk_tls = crate::postgres_rustls::MakeRustlsConnect::new(client_config);
         let tls = <MakeRustlsConnect as MakeTlsConnect<tokio::net::TcpStream>>::make_tls_connect(
             &mut mk_tls,
             host,