Refactor Praefect test server helpers

There were many variations of functions to build Praefect in the test code. This made tests less consistent and hard to understand. This refactor introduces a consolidated way to build Praefect servers (func runPraefect) and a function option struct (buildOptions) to allow customization/overriding of default components. Each default component has a corresponding default* function name.

There are also a number of new functions to make the code more readable.

Note: no functional changes have been made. All changes were made in test files.