feat: add topologySpreadConstraints to CoreDNS add-on

[thiagoluiznunes]

Context on the change

Recently at WildlifeStudios, we had a short temporary outage in CoreDNS in one of our clusters, since a single node crashed, and all CoreDNS pods were running on it.

So, to avoid that, we would like to set our own topologySpreadContraints parameters according to our user case.

What does this PR do?

This PR adds support for customizing the field topologySpreadConstraints in the template of the CoreDNS add-on.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: thiagoluiznunes / name: Thiago Luiz (1c14acf)

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[hakman]

/ok-to-test

[k8s-ci-robot]

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

Test name	Commit	Details	Required	Rerun command
pull-kops-test	1c14acf	link	true	/test pull-kops-test

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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