Improve Portal describe

[sunng87]

This is an issue we ran into in GreptimeDB.

According to postgres behavior, for extended protocol parameter types, we will prefer to use client given types. If client didn't provide parameter types, or the type oid is 0 (which is an empty type oid), we will use server types as fallback.

Our current behavior is using server types always, this may break client driver like JDBC when it tries to use a bigint for timestamp.

[sunng87]

I'm going to implement this from upstream sunng87/pgwire#356

We will only provide how to extract parameter and result types, the auto implementation of describe functions will follow postgres' logic.