feat: add restartPolicy to kube_pod_init_container_info metric

[changhyuni]

What this PR does / why we need it:

This PR adds a label to kube_pod_init_container_info to track the restartPolicy set in the init_container
With sidecar support starting with kubernetes 1.28, init_container can be used restartPolicy
This metric tells you which pods are using the sidecar feature

How does this change affect the cardinality of KSM: (increases, decreases or does not change cardinality)
adds a label that is never updated for a given init container

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: xonvanetta / name: Fabian Heib (efa46b4)
• ✅ login: changhyuni / name: loanshark (85e0401)

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[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: changhyuni
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