[BUG] Don't run long-lived testcases every day

[mbuechse]

There is one testcase, namely cncf-k8s-conformance, that has a lifetime of one year, not least because running it is quite demanding. It need not be run daily, and neither should it be.

• increase lifetime for kaas-networking-check as well
• make daily pipeline job smarter so that these testcase are not included in every run move these testcases from periodic-daily to periodic-weekly
• if necessary, modify scripts to accommodate this

[mbuechse]

On second thought: don't use two pipelines, because the weekly pipeline and the daily pipeline will run on the same day once per week, and then they will each create a cluster for the tests and tear the cluster down. So instead of 7x per week, we would then create the cluster 8x per week: 7x in the daily pipeline and 1x in the weekly pipeline.

I propose to stay on the daily pipeline, but to implement some logic that ensures that some of the tests are only run on Saturdays or so (or even on, say, on the first of each month).