chore: old op name LogicalGet can modify to Scan

[TCeason]

          Note: it's an old name. Better to modify to Scan in a new issue.

fn try_from(value: RelOperator) -> Result<Self> {
        if let RelOperator::Scan(value) = value {
            Ok(value)
        } else {
            Err(ErrorCode::Internal(
                "Cannot downcast RelOperator to LogicalGet",
            ))
        }
    }

Originally posted by @TCeason in #15215 (comment)

[TracyZYJ]

Please assign me :)