fix(db_api): use sqlparse to split DDL statements

[IlyaFaer]

Instead of simple str.split(";") method use more smart sqlparse package to split DDL statements executed in a form:

cursor.execute("""
    ddl_statement1;
    ddl_statement2;
    ddl_statement3;
""")

[IlyaFaer]

According to what I see in the sqlparse source code and documentation, it should work okay with GoogleSQL. Plus to the test case I've tried several types of DDL statements (interleaved tables, alters, indexes - cases, which seems complex to me). All was splitted correсtly.