[DBAL-1097] Fix foreign key constraint referential action on Oracle

Oracle only supports `CASCADE` and `SET NULL` referential actions for foreign key constraints. It also supports `NO ACTION` but it cannot be declared with an explicit `ON DELETE NO ACTION` clause. The complete clause has to be omitted in order to make it work.
This PR fixes supported referential actions and omits the referential clause if either action `NO ACTION` or `RESTRICT` is set for the foreign key constraint to create.