ast: provider builders for convenient programmatic construction

I have a use case where I'm generating SQL strings, and in general having `sqlparser::ast` is quite good, but the structs are particularly painful to construct programatically. It'd be interesting if the ast structs offered an optional feature that had https://github.com/elastio/bon builders derived to build them.

Maybe somebody will teach me how to safely construct strings that I can then parse (that'd be fine! I just am not generally eager to be doing string formatting to produce sql, particularly given I don't have full control over the identifiers). For now I am generally just doing this formatting, but I don't love it.

El issue señala sqlparser::ast y una feature opcional de builder derivada de bon como puntos de entrada; inspecciona cómo están definidas actualmente las estructuras AST y las features opcionales. El resultado debería ser un enfoque de builder acordado y utilizable para las estructuras AST relevantes, que reduzca la necesidad de formatear manualmente strings SQL.

Escrito por el modelo de indexación a partir del texto del issue.