Create a general include file to share between different job strategies
We want to use different assumptions and overall processes between third-party packages that are more suited for the model used in builddebs and an approach that will be more convenient for people developing our own software which also builds a debian package.
To that end:
- Move most of the logic to an include file we can share between different frontends
- Build stage now generates a tar archive with a descriptive name, which should be more user-friendly
- A "wmfdeb" pipeline is added that only triggers when a change is pused to the main branch modifying debian/changelog
- Also functions to upload/create a release attached to the deb file are added.
Change-Id: I90bdcc56de394ac62cc806e28dc59f56102c8838