Extract the kafka streams and flink use case and load generator
and commons dependencies to a convention plugin to reduce the
complexety of the main build gradle file.

Create convention plugins to reduce complexity of the root build.gradle file

Co-authored-by: Nico Biernat <stu209212@mail.uni-kiel.de>

Co-authored-by: Nico Biernat <stu209212@mail.uni-kiel.de>

Co-authored-by: Nico Biernat <stu209212@mail.uni-kiel.de>

Co-authored-by: Nico Biernat <stu209212@mail.uni-kiel.de>

Allow using a random scheduler

Closes #87

See merge request !61

Rearrange use case enumeration

Closes #72

See merge request !88

Single CI/CD pipeline definitions

Closes #51 and #124

See merge request !89