Split CI test execution into parallel jobs (OSOE-730)

[Piedone]

This is something for the future, when we'll have a lot more (UI) tests, I just wanted to record the idea.

Currently, the Tests step in the CI build takes 8-10 minutes under Ubuntu. We have 71 UI tests that take up the bulk of this time. Once we'll have a lot more and, we've exhausted other speed-up options, and we want to make this step faster, we could split the Tests step into two or more parallel jobs. I'd only do this for the Ubuntu build-and-test-larger-runners job.

This requires us to have at least 3 jobs: One that does everything up to Build and Static Code Analysis. Then, it'd upload the build artifacts. Two other (parallel) jobs then would be triggered, download the artifacts, and execute the tests.

We need to employ Cancel Workflow on Failure for each of these jobs still.

This would allow us to have two separate VMs running the tests in parallel.

Jira issue