Update AppCreds for SCS2, PCO Prod1,2,3,4, WaveStack.

[garloff]

The old ones have expired, these will last until the end of 2026.

[garloff]

OK, this should be done by the providers themselves, according to #1046. Agree on the approach, had unfortunately not seen it prior to renewing the ACs for this PR.
I was on this topic mainly because I wanted to ensure everything works well again after the changes on zuul in early January.

Options:

• We pragmatically merge it, repairing IaaS tests against SCS2, PCO Prod1-4, WaveStack (Noris) for now. Fixing the zuul runs, helping me to understand whether everything there is indeed looking good.
• The fact we address SCS2, PCO and WaveStack is helping them now. It does feel fair to me as they have been generous in giving us access for test, dev, demos, infra, ... in the past, so that's OK from my view.
• This still can and should be overwritten by ACs generated and managed by the providers soon.
• Or we don't merge, forcing all providers to act NOW. (Has the urgency reached them already?)

[mbuechse]

It's encrypted, so I have to trust you.