Support unnamed prepared statements (#635)

* Add golang test suite to reproduce issue with unnamed parameterized prepared statements

* Allow caching of unnamed prepared statements

* Passthrough describe on portals

* Remove unneeded kill

* Update Dockerfile.ci with golang

* Move out update of Dockerfiles to separate PR

src/messages.rs

@@ -1109,7 +1109,7 @@ pub struct Describe {
 
     #[allow(dead_code)]
     len: i32,
-    target: char,
+    pub target: char,
     pub statement_name: String,
 }