Add step to publish junit test results

[ErikRehmTT]

Describe the feature request

As a test engineer I want to see my test results within the Jenkins native views for test results.

Acceptance criteria

• new step to publish jUnit reports exists
• the step does not trigger the report generation -> its expected that the report is already in the report folder
• the step allows to set thresholds to set the build unstable or failed if the percentage of failed tests is above the thresholds
• option exists to override stage status based on threshold evaluation
• by default the step fails if no report was found, but its possible to disable this behavior
• the jUnit results are available in the test results sidebar entry (by using the jUnit plugin)
• new step is documented
• tests got extended on all test levels