Allow to override all the `parser..` methods.

We are building a new RDBMS that still has only partial support for the full `SQL` dialect of Postgres.

This means that we need to parse the strings, and then rule out everything we still do not support. It will be easier and probably faster if we can do:

```rust
// As is possible here
pub fn parse_statement(&mut self) -> Result {
let _guard = self.recursion_counter.try_decrease()?;

// allow the dialect to override statement parsing
if let Some(statement) = self.dialect.parse_statement(self) {
return statement;
}
....
}

// Make at least the major components overridable:
pub fn parse_table_and_joins(&mut self) -> Result {
if let Some(result) = self.dialect.parse_table_and_joins(self) {
return result;
}
...
...
```

Comienza con el parse_statement override existente mostrado en el issue y luego inspecciona parse_table_and_joins y la dialect interface para identificar cómo se despachan los parser methods. Define el conjunto completo de métodos que deberían poder sobrescribirse y verifica que el parsing compatible siga funcionando mientras un dialect puede interceptar esos entry points.

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