Kubeflow 1.9.1 Release Candidate 2

The release includes the following platform/manifests/security changes:

• Kubernetes 1.31 support
• The Documentation has been overhauled
• The automatic CVE scanning with Trivy on the master branch workflow now lets you download the scanning results
• Rootless efforts in contrib/security continue
• Revised authentication

We also updated the following components:

• Kubeflow Pipelines 2.3.0, which includes Argo Workflows 3.4
• Training Operator v1.8.1
• KServe 0.13.1
• model registry v0.2.5 alpha

Known issues / TODO :

• #2895