Create scripts for test artifacts release managment

[jan-goral]

Author the user story for this feature

As a developer, I want to have separated release of test artifacts for each pull request so CI can check my changes with proper artifacts without clash with other pull requests.

Is your feature request related to a problem? Please describe.
#849

Describe the solution you'd like
For asynchronous work, sometimes we need a dedicated GitHub release of test artifacts for the specific pull request. So:

• Add script or Gradle task for generating zip bundle with test artifacts
• Add Gradle task for publishing zip bundle as GitHub release. https://github.com/Flank/test_artifacts already contains source code for publishing artifacts, you can reuse it. This published release should relate to the git branch.
• Add Gradle task for downloading test artifacts from Github release. This task should use the branch name to determine the expected release. If no release for the given branch will be found, the artifacts from the main release should be used.

Additional context
This issue is the next step after #899