Metadata:

- Fixes ENG-1662
- Fixes ENG-1664
- Fixes ENG-1663

Adds the actor testing framework and implements some basic actor tests. The tests are:

- An actor that makes repeated deposits
- An actor that makes repeated transfers

For information on how the framework works, see [integration-tests/actor-tests/README.md](integration-tests/actor-tests/README.md).