Refactor the BaseQueryRewriter hierarchy

[chiaradiamarcelo]

The BaseQueryRewriter is used to rewrite a query written in Exasol's SQL dialect to an external data source's SQL dialect.

This class is a concrete class, and provides a rewrite method, but this method is overridden by several classes, and the re-implemented methods break the substitution principle.

This makes it harder to understand, especially when implementing a new SQL dialect, given that one makes the assumption that this BaseQueryRewriter provides a common implementation but it doesn't.

We should address this, probably by making this method abstract and delegating this responsibility to the sub-classes.