feature: add rename to DeltaItem trait and support rename for column/constraints of the table

[tyrchen]

Previously rename is not addressed. Due to the natural of the diffing, it will be treated as drop/create for the column/constraints if the only change is just name.

A new logic is added for specific case: if only one column/constraint is removed and one new column/constraint is added, we will check if this is a rename case.

// check if it is a case for rename
if self.added.len() == 1 && self.removed.len() == 1 {
    let added = self.added.iter().next().unwrap();
    let removed = self.removed.iter().next().unwrap();
    let result = removed.to_owned().rename(item, added.to_owned())?;
    if !result.is_empty() {
        migrations.extend(result);
        is_rename = true;
    }
}

[tyrchen]

Fixed #3