Add unique indexes to derived tables

[Emiel Verkade]

Describe the feature

We use the unique_key parameter in the config of many derived tables (see here), but this seems to have no actual effect outside of dbt's snapshot functionality (see here). We should use indexes to actually add a unique key index to Postgres to improve performance (see here).

So in short, we should remove the unique_key parameter from the tables, and introduce indexes with the unique key index in our derived tables.

[Ryan Hill]

unique_key is required for the upsert on a merge method, but we should add the other stuff