simplify the ci pipeline to the bare minimum
we don't need to test several versions of gcc and mysql; they are all already tested in the pipeline for hercules so re-testing in the repo for every single merge request is silly and takes a lot of time
- strip the pipeline to the essentials
- make use of directed acyclic graph to execute linting and testing at the same time
closes evol-hercules#8 (closed)
Edited by gumi