Simplify e2e teardown for ephemeral KinD clusters

[karangupta982]

Closes #122

Simplifies e2e teardown for ephemeral KinD clusters.

• Keep the EtcdCluster/EtcdMember cleanup required while the operator is running.
• Remove redundant teardown steps for the operator, CRDs, namespace, Prometheus, and cert-manager.
• Destroy the KinD cluster directly after the required etcd resource cleanup.
• Preserve ETCD_E2E_SKIP_TEARDOWN behavior.

Since the KinD cluster is ephemeral, destroying it already removes the resources installed in the cluster.

[kubernetes-prow]

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[kubernetes-prow]

Hi @karangupta982. Thanks for your PR.

I'm waiting for a etcd-io 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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[karangupta982]

Hi @ArkaSaha30 , just following up on this PR. Please let me know if there is anything I should modify or address.
Thanks!