Grouping statement enum by macro-categories

At this time, the statements enum is massive and includes all SQL statements. What if we were to create sub-enum categories, such as DML, DDL DQL, DCL, TCL, SCL, PSM and so on?

This would clearly break APIs, but it would make much more manageable to work with statements, expecially in the cases where only a subset of the statements are desidered.

Luca

Start by locating the statements enum and reviewing its public API and usages. Define the proposed SQL macro-categories and assess the API breakage and compatibility implications; the work is complete when the category structure and affected interfaces are agreed and covered by the relevant parser tests.

Written by the indexing model from the issue text.