e2e testing: cleanup (remove edge tests and other stale files)

[jenshu]

• remove edge / glooctl / validation tests under test/kubernetes/e2e - remove edge tests #10527
• remove cilium from setup-kind (used to test leader election) - remove cilium from setup-kind script #10551
• remove skv2 dep - Remove skv2 dep in e2e tests #10556
• remove unneeded flags and clients in test/kubernetes/e2e More test cleanup #10578
• rename gloogateway => kgateway e2e test helpers: rename gloogateway #10582
• remove test/kube2e (may need to refactor helpers if they are still used elsewhere) filed new issue e2e testing: remove test/kube2e #10604
• remove the examples directory if it's no longer needed (see PR comment) edit: we might want to keep this
• remove test/kubernetes/e2e dependence on helpers from kube2e - Remove kube2e dep from test/kubernetes/e2e #10587

[jenshu]

did a bunch of cleanup (PRs linked above); this one can be closed