Set up potential Gradle configuration in another repository

### User Story

As a developer of Sleeper, I want to be able to run parts of the build quickly on the command line, so that I can get fast feedback.

### Description / Background

In another repository we've got a Gradle build with a similar multi-module setup. We'd like to adapt this to make it as suitable as we can to potentially apply to the main Sleeper repository.

We've seen this save a lot of time compared to Maven, as it includes incremental builds and is generally a lot quicker.

No target repository, files, or existing Gradle entry point are named. Start by locating the referenced repository and comparing its multi-module build with Sleeper's current build; determine which parts could support faster command-line feedback and what validation would show that the setup is suitable for potential use in the main repository.

Written by the indexing model from the issue text.