[Snowflake] Create primary keys in the destination if they exist in the schema

[rudolfix]

Backrgound
Snowflake allows to add hints to columns for PRIMARY KEY and UNIQUE. those hints are not enforced but used for query planning. We want to add those hints to SQL we generate - like we do for postgres or duckdb.

Tasks

1. • make behavior optional and switched off by default
2. • generate PRIMARY KEY and UNIQUE hints.
3. • make sure to test what happens if we set both
4. • tests multi column hints. not sure if they are supported

More info
https://docs.snowflake.com/en/sql-reference/constraints-overview
It seems that multi column hints must be generated as separate SQL statement. That may need some changes in sql_job_client. there was support for that but never used