Update kserve and add some fixes

[wjayesh]

• Version upgraded from 1.6 to 1.9 for kserve terraform module (knative & istio).
• graceful failure of the kubectl delete command when no resources exist.
• Add workload identity annotation to kubeflow's pipelin-runner service account.

[strickvl]

@wjayesh what still needs doing for this PR? wondering if we should get it finished or close it?

[wjayesh]

I'm not sure if we support kserve any longer. if we do, then we should complete the PR, otherwise close it.
For completing, I think we need to port changes from the kserve-module in this PR to the current kserve module and then test if the deployment works. I'm happy to assist with that but might need at least until next week to get to this.

[strickvl]

mlstacks supports kserve, but zenml no longer supports it, so perhaps we should also drop from mlstacks as well. WDYT? @stefannica ?