fix: duplication on adding policies to db

[ndodanli]

No description provided.

[casbin-bot]

@tangyang9464 @JalinWang @imp2002 please review

[hsluoyz]

@ndodanli fix the CI:

[ndodanli]

@hsluoyz
There is a column naming difference between databases that i think xorm column naming is responsible for this. For example, 'pgtype' for mysql and 'pg_type' for postgres. I determine by checking driver name but setting a fixed column name for all databases is better, but setting fixed column names is not up to me.

Also i saw a usage for directly calling "pgtype" on UpdateFilteredPolicies()(adapter.go:550)->queryString()(adapter.go:643) and this can cause problems on postgres. You might want to check on this.

[hsluoyz]

@ndodanli this PR is becoming more complicated, even involving home-made column names now. And the tests still failed. I have no confidence for this PR. So closed here. You can do de-duplication on your side anyway.