feat: add flags for changing leader election lease duration, renew deadline, retry period

[olyazavr]

Description
We've been seeing slow lease updates in our very loaded clusters that lead to a ton of container restarts. We've made changes to relax the lease settings on other kube components, but I found no such settings available for karpenter.

This adds 3 configurable flags/env vars to control leader election:

• lease duration: leader-election-lease-duration, LEADER_ELECTION_LEASE_DURATION, default 15s
• renew deadline: leader-election-renew-deadline, LEADER_ELECTION_RENEW_DEADLINE, default 10s
• retry period: leader-election-retry-period, LEADER_ELECTION_RETRY_PERIOD, default 2s

Defaults are taken from the controller defaults, so no change to existing behavior. Descriptions are copied from other kube components with these settings.

How was this change tested?
I deployed this patch into our own cluster with extra logging to ensure the (higher than default) values were taken and verified that the slow lease updates and sporadic container restarts went away

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: olyazavr / name: Olga Shestopalova (2936362)

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[coveralls]

Pull Request Test Coverage Report for Build 19541428786

Details

• 6 of 9 (66.67%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.005%) to 81.103%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/operator/operator.go	0	3	0.0%

Totals
Change from base Build 19342868454:	0.005%
Covered Lines:	11794
Relevant Lines:	14542

---

💛 - Coveralls

[k8s-ci-robot]

@olyazavr: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

In response to this:

/retest

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