[occm] Make hostNetwork configurable in the Helm chart

[zwindler]

What this PR does / why we need it:

Makes hostNetwork configurable in the cloud controller manager Helm chart by adding a hostNetwork value (default: true).

Currently hostNetwork: true is hardcoded in the DaemonSet template. This makes sense for the default use case where OCCM manages nodes and routes, but for users who only run a subset of controllers (e.g. just the service controller for Octavia LB), hostNetwork is an unnecessary privilege escalation. The controller only needs to talk to the Kubernetes API and the OpenStack API, both reachable from pod networking.

This PR also fixes dnsPolicy to automatically use ClusterFirstWithHostNet when hostNetwork is true, as recommended by the Kubernetes docs:

ClusterFirstWithHostNet: For Pods running with hostNetwork, you should explicitly set its DNS policy to ClusterFirstWithHostNet. Otherwise, Pods running with hostNetwork and "ClusterFirst" will fallback to the behavior of the "Default" policy.

The current chart uses dnsPolicy: ClusterFirst with hostNetwork: true, which falls back to host DNS. This has no practical impact today since OCCM doesn't resolve cluster-internal service names, but it's technically incorrect.

Which issue this PR fixes(if applicable):

N/A

Special notes for reviewers:

The default remains hostNetwork: true, so this is a no-op for existing deployments.

This PR contains two distinct changes: the hostNetwork toggle and the dnsPolicy fix. If you'd prefer to keep them separate, I can split this into two PRs.

Release note:

[openstack-cloud-controller-manager] Make hostNetwork configurable in the Helm chart (default: true)

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