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

libs/proxy/postgres-protocol2/src/escape/test.rs

@@ -0,0 +1,17 @@
+use crate::escape::{escape_identifier, escape_literal};
+
+#[test]
+fn test_escape_idenifier() {
+    assert_eq!(escape_identifier("foo"), String::from("\"foo\""));
+    assert_eq!(escape_identifier("f\\oo"), String::from("\"f\\oo\""));
+    assert_eq!(escape_identifier("f'oo"), String::from("\"f'oo\""));
+    assert_eq!(escape_identifier("f\"oo"), String::from("\"f\"\"oo\""));
+}
+
+#[test]
+fn test_escape_literal() {
+    assert_eq!(escape_literal("foo"), String::from("'foo'"));
+    assert_eq!(escape_literal("f\\oo"), String::from(" E'f\\\\oo'"));
+    assert_eq!(escape_literal("f'oo"), String::from("'f''oo'"));
+    assert_eq!(escape_literal("f\"oo"), String::from("'f\"oo'"));
+}