Remove lint, test and test-e2e GitHub workflows

[ivanvc]

These workflows have already been migrated to Prow jobs.

Part of #21.

[jmhbnz]

LGTM - Thanks for the help migrating these workflows @ivanvc 👍🏻

[ahrtr]

LGTM

Thanks

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[ahrtr]

@ivanvc after merging this PR, it seems the main branch only runs post-etcd-operator-lint when we merge each PR. I think we should also run all workflow checks on main when merging a PR.

[ivanvc]

@ivanvc after merging this PR, it seems the main branch only runs post-etcd-operator-lint when we merge each PR. I think we should also run all workflow checks on main when merging a PR.

Sorry, I followed the same approach we have in the etcd repo.