Investigate `includegit-gradle-plugin` as a helper for our multi-repository development

[alexander-yevsyukov]

https://github.com/melix/includegit-gradle-plugin

It looks promising, as it automates some pieces of work. For example, it can be useful for testing config updates on the subprojects like core-java, mc-java, or gcloud

Unfortunately, one if of the limitations of this settings plugin is that it does not handle plugin substitutions.