feat: add ability to configure Pod's hostNetwork, dnsConfig, dnsPolicy

[druchoo]

Hello, thank you for snapshot-controller Chart. Please review for AWS EKS with custom CNI compatibility. Fixes #42

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When using a custom CNI (such as Weave or Calico) on Amazon EKS, the webhook cannot be reached.

Internal error occurred: failed calling webhook "snapshot-validation-webhook.snapshot.storage.k8s.io": failed to call webhook: Post "https://snapshot-validation-webhook.kube-system.svc:443/volumesnapshot?timeout=2s": Address is not allowed

This happens because the control plane cannot be configured to run on a custom CNI on EKS, so the CNIs
differ between control plane and worker nodes.

To address this, the webhook can be run in the host network so it can be reached.

webhook:
  hostNetwork: true
  dnsPolicy: ClusterFirstWithHostNet

[WanzenBug]

Just some simplification on the templates, otherwise I'm ready to merge this.

As a side note, I was under the impression that EKS clusters already have the snapshot controller deployed from the start.

[WanzenBug]

LGTM