feat: add new init function for Connector

[longxiaofei]

related issue: #688

from sqlalchemy import create_engine
from pygwalker.data_parsers.database_parser import Connector

# sqlalchemy url
connector = Connector(database_url, view_sql)

# sqlalchemy engine
engine = create_engine(database_url)
connector = Connector.from_sqlalchemy_engine(engine, view_sql)

# sqlalchemy connection(adapt memory duckdb)
engine = create_engine(database_url)
with engine.connect() as conn:
    connector = Connector.from_sqlalchemy_connection(conn, view_sql)