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/proxy/tests/mod.rs

@@ -14,7 +14,6 @@ use rustls::pki_types;
 use tokio::io::DuplexStream;
 use tokio_postgres::config::SslMode;
 use tokio_postgres::tls::{MakeTlsConnect, NoTls};
-use tokio_postgres_rustls::MakeRustlsConnect;
 
 use super::connect_compute::ConnectMechanism;
 use super::retry::CouldRetry;
@@ -29,6 +28,7 @@ use crate::control_plane::{
     self, CachedAllowedIps, CachedNodeInfo, CachedRoleSecret, NodeInfo, NodeInfoCache,
 };
 use crate::error::ErrorKind;
+use crate::postgres_rustls::MakeRustlsConnect;
 use crate::types::{BranchId, EndpointId, ProjectId};
 use crate::{sasl, scram};