This commit basically refactors the ami resolution code to make use of
the new PgAwsAmi entity. Since we will have multiple regions and
multiple versions of pg, we need to be able to programmatically modify
that logic. If we continued the old way, we would need to add new config
variables for new regions and versions.
We are also removing billing rates regarding us-east-1, us-west-1 since
these are not enabled, yet. This means we need to refactor the tests
referencing us-east-1 as well.
f162c2c68b