[occm] test: add loadbalancer servicemonitor regression

[jihyun-huh]

What this PR does / why we need it:

Hi maintainers,
this PR adds renderering level regression coverage for the OCCM Helm chart ServiceMonitor behavior fixed by #3039

currently, the existing chart CI runs ct lint with the default values, where serviceMonitor.enabled is disabled. and it therefore does not exercise or semantically validate the ServiceMonitor, metrics Service, and DaemonSet wiring.

The new tests verify this things:

• add metric resources and public metrics access remain disabled by default
• enabling serviceMonitor creates matching Service and ServiceMonitor resources
• the Service selects the OCCM DaemonSet pods
• update document that deprecated bearerTokenFile authentication is not now used
• update OCCM exposes and authorizes /metrics only when monitoring is enabled

references:

• https://github.com/kubernetes/ingress-nginx/blob/main/charts/ingress-nginx/tests/controller-servicemonitor_test.yaml
• https://github.com/kubernetes-sigs/descheduler/blob/master/.github/workflows/helm.yaml
• https://github.com/kubernetes-sigs/descheduler/blob/master/charts/descheduler/tests/servicemonitor_test.yaml

Which issue this PR fixes(if applicable):
Follow-up to #3039, adds regression coverage for #3144

Special notes for reviewers:

helm-unittest is pinned to the immutable v1.0.3 commit, because this is the latest release compatible with the Helm v3.10.0 currently used by the chart workflow.

The suite passes against current master branch.
against the parent of #3039, it fails on the previous selector mismatch, deprecated bearer token configuration, and missing metrics authorization flag.

also, this is a renderering level test and does not require a Kubernetes, Prometheus, or OpenStack environment.

Release note:

NONE

[kubernetes-prow]

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[kubernetes-prow]

Hi @jihyun-huh. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work.

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[jihyun-huh]

Hi @gouthampacha @kayrus, could one of you please add /ok-to-test when you have a chance? This PR only adds Helm regression coverage for the ServiceMonitor fix merged in #3039. Thanks!