[Snowflake]Show roles not fully implemented

[MasterKuat]

show_roles rule do not handle all available syntax.

Show roles syntaxe as defined in https://docs.snowflake.com/en/sql-reference/sql/show-roles SHOW [ TERSE ] ROLES [ LIKE '' ] [ IN CLASS <class_name> ] [ STARTS WITH '<name_string>'] [ LIMIT [ FROM '<name_string>' ] ]