Extract internal Gradle Service Injection framework into separate subprojects

[alllex]

Classes like ServiceRegistry and related machinery currently live in the bloated :base-services project. Since they provide an independent aspect of the Gradle architecture they should be located in their own subproject.

Let's split out a separate API subprojects as well, so subprojects that only want to declare services provided and consumed might do so without depending on the implementation.

The types from :java-language-extensions related to scopes should be moved to the new service registry API module, too.