Add pretty print AST for debugging AST in CLI

[krishvishal]

Why: @alpaylan wanted a way to pretty print AST in CLI for debugging purposes.

Usage and output:

Limbo v0.0.14
Enter ".help" for usage hints.
Connected to a transient in-memory database.
Use ".open FILENAME" to reopen on a persistent database
limbo> .pprint "SELECT 1;"

=== Input SQL ===
SELECT 1;

=== AST ===
Select(
    Select {
        with: None,
        body: SelectBody {
            select: Select(
                SelectInner {
                    distinctness: None,
                    columns: [
                        Expr(
                            Literal(
                                Numeric(
                                    "1",
                                ),
                            ),
                            None,
                        ),
                    ],
                    from: None,
                    where_clause: None,
                    group_by: None,
                    window_clause: None,
                },
            ),
            compounds: None,
        },
        order_by: None,
        limit: None,
    },
)
limbo> 

[PThorpe92]

is this used just the one time on ln436?

[krishvishal]

Yes. Its only used once.

[krishvishal]

Fixed merge conflicts.