Implement maintaining multiple lease support for benchmark

[serathius]

Please read https://github.com/etcd-io/etcd/blob/main/CONTRIBUTING.md#contribution-flow.

[k8s-ci-robot]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: serathius

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[k8s-ci-robot]

PR needs rebase.

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[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed after 21 days if no further activity occurs. Thank you for your contributions.

[k8s-ci-robot]

@serathius: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci-etcd-robustness-release36-amd64	3e3949d	link	true	/test ci-etcd-robustness-release36-amd64
ci-etcd-robustness-release35-amd64	3e3949d	link	true	/test ci-etcd-robustness-release35-amd64
ci-etcd-robustness-release34-amd64	3e3949d	link	true	/test ci-etcd-robustness-release34-amd64

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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