Create reusable transaction generator for test apps

- Each test app has its own uniquely rolled setup to generate transactions at a certain rate
- A reusable utility object to perform this would be simple enough to create, and significantly decrease the complexity of existing and new test apps
- I think it makes sense to create a corresponding config class that can be reused, that allows the developer to configure the following aspects of transaction generation:
- total rate
- ramp up period

Compare how each test app currently sets up transaction generation and identify the shared behavior to extract. Define the reusable utility and configuration around the stated total rate and ramp-up period; done means existing and new test apps can use the shared approach without their own rolled setup.

Written by the indexing model from the issue text.