[NPE] Add GCP Pubsub Support

[ojameso]

This adds GCP PubSub support.

Adds both Chore::Queues::PubSub::Consumer and Chore::Queues::PubSub::Producer. this can be configured numerous ways. Interesting notes regarding configuration have been added to the README.

Breaking change

1. Moves AWS-SQS to dev-dependency and not runtime since we can now use either AWS or GCP.
2. Drops support for Ruby 2.7

Nonbreaking change

1. Add PubSub support
2. Queue creation tasks now separate into create_sqs/create_pubsub tasks.

Testing

• TIAB - Was able to create a test job in tapjoyserver to read/write form the Queue.

[captainkevron]

Couple small questions. I am not very familiar with the Chore architecture, so I mostly used the SQS implementation as a reference to compare against. Nice work on the README.md updates.

[obrie]

All of my comments are nice-to-have cleanup. Functionally everything looks good here. Going to approve as-is and leave it up to you how much cleanup you want to do.

[adnissen]

lgtm