TOP-1344: Nightly CI/CD pipeline

This MR combines !111 (merged) and !112 (merged). In short:

• Added the ability to publish test results to Xray
• Renamed the existing tests:regression CI job to tests:aa05 and linked it to the AA0.5 FAT Xray Test Plan
• Reworked the mechanism to switch between short/full scan durations by adding a dedicated environment variable
• Disabled non-test CI jobs in scheduled pipeline runs

All of the above enable us to perform nightly regression testing using full scan durations and publishing the results to Xray. We can reuse the same mechanism to run release pipelines triggered by ska-low-csp as well by passing the necessary variables.

The actual pipeline schedule is configured on this page: https://gitlab.com/ska-telescope/ska-low-csp-test/-/pipeline_schedules.