The following liquibase changeset does not work as expected

```xml
        <createTable tableName="test">
            <column name="id" type="SERIAL">
                <constraints nullable="false" primaryKey="true"/>
            </column>
        </createTable>
```

This changeset results in sql

```sql
CREATE TABLE test (id INTEGER NOT NULL, CONSTRAINT TEST_PKEY PRIMARY KEY (id));
```

In liquibase 3.6.3 and earlier the type `SERIAL` was used for the column which means that a sequence is automatically included.

This issue seems to be caused by #874
It appears that SERIAL columns are replaced by INT, however liquibase does reconize that this column type is an auto increment column.

It would be acceptible if the generated sql would be

```sql
CREATE TABLE test (id INTEGER GENERATED BY DEFAULT AS IDENTITY NOT NULL, CONSTRAINT TEST_PKEY PRIMARY KEY (id));
```


public class CreateTableChange extends AbstractChange implements ChangeWithColumns<ColumnConfig> {
    private List<ColumnConfig> columns;
    private String catalogName;
    private String schemaName;
    private String tableName;
    private String tablespace;
    private String remarks;
    public CreateTableChange() {
        super();
        columns = new ArrayList<>();
    }
    @Override
    public ValidationErrors validate(Database database) {
        ValidationErrors validationErrors = new ValidationErrors();
        validationErrors.addAll(super.validate(database));
        if (columns != null) {
            for (ColumnConfig columnConfig : columns) {
                if (columnConfig.getType() == null) {
                    validationErrors.addError("column 'type' is required for all columns");
                }
                if (columnConfig.getName() == null) {
                    validationErrors.addError("column 'name' is required for all columns");
                }
            }
        }
        return validationErrors;
    }
    @Override
    public SqlStatement[] generateStatements(Database database) {
        CreateTableStatement statement = generateCreateTableStatement();