Always wrap statement in a named struct

In [GreptimeDB](https://github.com/GreptimeTeam/greptimedb/blob/v0.7.1/src/sql/src/statements/delete.rs), we write code like:

```rust
#[derive(Debug, Clone, PartialEq, Eq, Visit, VisitMut)]
pub struct Delete {
// Can only be sqlparser::ast::Statement::Delete variant
pub inner: Statement,
}
```

It's because in sqlparser-rs, these statement variants are unnamed struct:

```rust
Delete {
/// Multi tables delete are supported in mysql
tables: Vec,
/// FROM
from: Vec,
/// USING (Snowflake, Postgres, MySQL)
using: Option>,
/// WHERE
selection: Option,
/// RETURNING
returning: Option>,
},
```

I wonder if we can always wrap statement in a named struct so that downstream software can reuse the AST and impls (like for Display) more smoothly.

I don't know if it's a breaking change or we're generally OK with this.

Ref - https://github.com/GreptimeTeam/greptimedb/issues/3646

Comienza revisando las definiciones de statements en el sqlparser AST y el wrapper posterior mostrado en src/sql/src/statements/delete.rs de GreptimeDB. Comprueba cómo el código posterior implementa o consume Display y otros traits del AST, y determina después el impacto en la compatibilidad de envolver cada variante de statement. Se considera completado cuando exista un diseño documentado o un plan de implementación aceptado que aborde las cuestiones de reutilización y los breaking changes.

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