gitlab-ci: Unify wording and clarify architecture

Our current CI structure doesn't make a distinction between building, packaging and distributing. I'm fine with this. But this wouldn't be a problem only if the nomenclatures weren't, with due respect, nonsensical.

• Why appimage is the only job to not begin with inkscape? It seems a problem of parallelism in the wording. So, i fixed it.
• Why windows have a dist sufix? This makes us assume that other jobs are incomplete (not packaged). So, i fixed it.
• Also, the artifact architecture is the most ambiguous. I had to check each script to find out. So, i added it to the CI.

I gently ask for developers' understanding of the fact that new contributors accustomed to other organized CIs (eg: GIMP, OBS) really have no fast way of knowing what the artifacts of Inkscape jobs are about.

It is not my intention to criticize the CI built gradually by the community. I am open to clarifications, if any, before the MR.