Support for sidecar containers

[alculquicondor]

What happened:

We are currently treating sidecar containers as regular initContainers. However, sidecar containers continue running until the pod completes https://kubernetes.io/docs/concepts/workloads/pods/sidecar-containers/

Note that this feature is beta since kubernetes v1.29

What you expected to happen:

To account for the usage of sidecar containers.

Anything else we need to know?:

The function should look similar to this: https://github.com/kubernetes/kubernetes/blob/ae02f87bb47cd3e10e702ffe19225ff2dba73578/pkg/api/v1/resource/helpers.go#L50

However, we should not directly use that function, as it doesn't have stability guarantees and the kubernetes module might have non-trivial dependencies.

We could, in parallel, start a different effort to move this function to some other place more reusable, like https://github.com/kubernetes/kubernetes/tree/master/staging/src/k8s.io/component-helpers/scheduling

Environment:

• Kubernetes version (use kubectl version): v.129
• Kueue version (use git describe --tags --dirty --always):
• Cloud provider or hardware configuration:
• OS (e.g: cat /etc/os-release):
• Kernel (e.g. uname -a):
• Install tools:
• Others:

[alculquicondor]

/assign @trasc

[alculquicondor]

I opened the issue upstream kubernetes/kubernetes#124537

[IrvingMg]

/assign