Submit the code from "release" branch to a separate OBS project

[lslezak]

Problem

• We need a separate OBS project for releasing the Agama

Solution

• Created systemsmanagement:Agama:Release OBS project
• Modified the submission GitHub Action so it runs also in the release branch
• That branch uses the OBS_PROJECT_RELEASE GitHub variable which points to the OBS project above
• The GitHub action then either uses the OBS_PROJECT variable (master branch) or OBS_PROJECT_RELEASE variable (release branch)

Testing

• The actions work fine, see an example run
• The submission to openSUSE Factory has not been tested (too complex, needs separate Git and OBS fork, there is a minimal change in the code so I expect it to work)

[imobachgs]

Code-wise it looks good. But, please, update the documentation in the website repository (and drop this one).

[imobachgs]

Oh, this obs_integration.md file is a leftover. Please, update the obs_integration.md from the website repository instead.