Add needs-rebase plugin for etcd project

[ArkaSaha30]

This PR will add needs-rebase plugin to the etcd project which will add needs-rebase to a PR that requires a rebase and removes it once it's rebased with the concerned branch.

Issue link: etcd-io/etcd#18110

[ArkaSaha30]

cc @jmhbnz @ahrtr

[MadhavJivrajani]

/approve
/hold

One tiny comment, lgtm after that!

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ArkaSaha30, MadhavJivrajani

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[ahrtr]

/lgtm

Thanks

[MadhavJivrajani]

/hold cancel

[k8s-ci-robot]

@ArkaSaha30: Updated the plugins configmap in namespace default at cluster test-infra-trusted using the following files:

• key plugins.yaml using file config/prow/plugins.yaml

In response to this:

This PR will add needs-rebase plugin to the etcd project which will add needs-rebase to a PR that requires a rebase and removes it once it's rebased with the concerned branch.

Issue link: etcd-io/etcd#18110

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