Rotate kubectl skew and soak jobs from k8s-stable1 to k8s-stable2

The k8s-stable1 marker (https://storage.googleapis.com/k8s-release-dev/ci/k8s-stable1.txt)
is no longer being published, causing test failures in sig-release-master-blocking
and other jobs that depend on it.

This change rotates all affected jobs to use k8s-stable2 instead:
- All sig-cli kubectl skew test jobs (stable1 → stable2)
- All sig-cloud-provider soak test jobs (stable1 → stable2, stable2 → stable3, stable3 → stable4)

The rotation also properly handles cross-version skew tests:
- stable1-stable2 → stable2-stable3
- stable2-stable1 → stable3-stable2

This unblocks the failing tests while the release team investigates why
the k8s-stable1 marker stopped being published.

Ref: https://kubernetes.slack.com/archives/C2GL57FJ4/p1762167598568149

Signed-off-by: Sascha Grunert <[email protected]>

Author: saschagrunert