Expanded the filtering mechanism beyond commenting on extensions, to address new features in Postgres v17 which are not available in our SG Cloud pg v16 databases, as well as SQL queries / commands which break Google Cloud SQL's very fragile import.

Also renamed "primary.sql" to "pgsql.sql" to be consistent, as this is the only place across our entire codebase that this database got yet-another-name.

Test plan

Tested on customer Cloud migration

Updated unit tests

Updated process docs for IE team performing these migrations