Require default role to be set for using connection impersonation (#33444)

* throw exception if impersonated db doesn't have default role

* change text in snowflake plugin file

* fix bugs and add tests

* FE changes

* inline enabled? call

* add new driver feature connection-impersonation-requires-role

* use variant=brand

* break out impersonation-enabled-for-db? into a defenterprise helper function