refactor maven project

Bug: T310626

This MR introduces the following changes in project structure:

1. renaming the project groupId.
2. refactoring to maven multi module.
   • re-arrange pom dependencies for parent/children.
3. reformatting code with 4 spaces (see https://gitlab.wikimedia.org/-/snippets/27 https://gerrit.wikimedia.org/r/c/wikimedia/discovery/discovery-maven-tool-configs/+/805394)
4. version bump to Scala 2.13

Tagging @otto @dcausse @tchin