[Go] Implement constraint metadata in GetObjects

[Mandukhai-Alimaa]

ERROR validation/tests/test_connection.py::TestConnection::test_get_objects_constraints_foreign[snowflake:snowflake] - NotImplementedError
ERROR validation/tests/test_connection.py::TestConnection::test_get_objects_constraints_primary[snowflake:snowflake] - NotImplementedError
ERROR validation/tests/test_connection.py::TestConnection::test_get_objects_constraints_unique[snowflake:snowflake] - NotImplementedError