Amend circleci resource_classes (#3561)
Amend circleci resource_classes (#3561)

* Use circleci resource_classes

Improve speed on some jobs while not consuming
as much resource/circleci-credits on others

see https://circleci.com/docs/2.0/configuration-reference/#resource_class

 - add large resource rspec
 	 10000+ tests taking 15 minutes. is a bottleneck!

 - add small resource for basic-executor and cloud-platform-executor
   These typically only need a small amount of resource but some jobs
   may require more (like build and push build). Specific jobs using
   one of these executors can have their resource overriden at the
   resource level.
ministryofjustice/advocate-defence-payments,ministryofjustice/advocate-defence-payments,ministryofjustice/advocate-defence-payments,ministryofjustice/advocate-defence-payments