[feature] allow pretty-printing

[lovasoa]

In rust, the Display trait allows specifying an "alternate" display style for every type:

https://doc.rust-lang.org/std/fmt/struct.Formatter.html#method.alternate

I suggest using this to allow "pretty-printing" SQL statements, including newlines.

Currently, long queries printed by sqlparser are hardly human-readable, since they are displayed as a single long line of text. We could allow displaying them with newlines between keywords and expressions when they are printed with {:#}

this is also a potential more feasible alternative to #1634

I could implement this myself.

What do you think, @alamb , @iffyio ?

[alamb]

If the idea is that {:#} printing of AST nodes would result in printing a "pretty" version of the sql statements (potentially with newlines, etc) sounds like a great idea to me

[lovasoa]

follow-up tracking issue in #1850