Tests for how we handle parameters of different types

In the cases that I think are problematic, the strangeness results from the commented code in `PostgresBaseOperatorStatement.getParameterTypes`. In my example, an odd `PostgresType` `VARCHAR()/int4`.

Perhaps things would be more robust if instead it were represented as a straightforward decoder, from bytes to `ValueSource`, according to what the client is expected to send. Often, just something that wraps a string. And then, separately, as an optional conversion from that to what the query wants for its parameter.

That is, instead of trying to determine a good conversion dynamically with a `java.lang.Object`, determine it at prepare time with only meta-data and just execute it here.