validate row: Hash Validation Fails on Oracle Versions < 12c

When using `-hash` the generated SQL uses a STANDARD_HASH() SQL function.
Test table:
```
create table dms_test_cases.tab_id (id number(2) not null primary key);
insert into dms_test_cases.tab_id values (1);
commit;
```

Command:
```
data-validation validate row -sc=ora_local -tc=ora_local \
--filter-status=fail -tbls=dms_test_cases.tab_id -pk=id -hash='id'
```

Exception:
```
sqlalchemy.exc.DatabaseError: (cx_Oracle.DatabaseError) ORA-00904: "STANDARD_HASH": invalid identifier
[SQL: SELECT t0.hash__all, t0.id
FROM (SELECT t1.id AS id, t1.cast__id AS cast__id, t1.ifnull__cast__id AS ifnull__cast__id, t1.rstrip__ifnull__cast__id AS rstrip__ifnull__cast__id, t1.upper__dvt_calc_col_0 AS upper__dvt_calc_col_0, t1.concat__all AS concat__all, lower(standard_hash(t1.concat__all, 'SHA256')) AS hash__all
FROM (SELECT t2.id AS id, t2.cast__id AS cast__id, t2.ifnull__cast__id AS ifnull__cast__id, t2.rstrip__ifnull__cast__id AS rstrip__ifnull__cast__id, t2.upper__dvt_calc_col_0 AS upper__dvt_calc_col_0, upper__dvt_calc_col_0 AS concat__all
FROM (SELECT t3.id AS id, t3.cast__id AS cast__id, t3.ifnull__cast__id AS ifnull__cast__id, t3.rstrip__ifnull__cast__id AS rstrip__ifnull__cast__id, upper(t3.rstrip__ifnull__cast__id) AS upper__dvt_calc_col_0
FROM (SELECT t4.id AS id, t4.cast__id AS cast__id, t4.ifnull__cast__id AS ifnull__cast__id, rtrim(t4.ifnull__cast__id) AS rstrip__ifnull__cast__id
FROM (SELECT t5.id AS id, t5.cast__id AS cast__id, coalesce(t5.cast__id, :param_1) AS ifnull__cast__id
FROM (SELECT t6.id AS id, CAST(t6.id AS VARCHAR2(4000 CHAR)) AS cast__id
FROM dms_test_cases.tab_id t6) t5) t4) t3) t2) t1) t0]
```

The problem expression is:
```
lower(standard_hash(t1.concat__all, 'SHA256')) AS hash__all
```

Oracle 11g:
```
select standard_hash('Hello', 'SHA256') from dual
*
ERROR at line 1:
ORA-00904: "STANDARD_HASH": invalid identifier
```

Oracle > 11g:
```
SQL> select standard_hash('Hello', 'SHA256') from dual;

STANDARD_HASH('HELLO','SHA256')
----------------------------------------------------------------
185F8DB32271FE25F561A6FC938B2E264306EC304EDA518007D1764826381969
```

There is no standard alternative for 11g so I think our options are:

1. Document that `-hash` is not valid for Oracle versions prior to 12c
2. Throw an informational exception when `-hash` is used on Oracle versions prior to 12c