fix: topologySpreadConstraint fields in structured logs

[SataQiu]

There is a problem with the log display due to the use of non-exported fields： https://github.com/kubernetes-sigs/descheduler/blob/f0f7ebbe9af680b338709391cf1c0da7c2270ce5/pkg/framework/plugins/removepodsviolatingtopologyspreadconstraint/topologyspreadconstraint.go#L220

Without this patch the tsc is printed as empty {}:

I1212 08:34:36.666387       1 topologyspreadconstraint.go:230] "Skipping topology constraint because it is already balanced" constraint={}

With this patch:

I1212 08:41:10.178744       1 topologyspreadconstraint.go:221] "Skipping topology constraint because it is already balanced" constraint={"MaxSkew":1,"TopologyKey":"topology.kubernetes.io/zone","Selector":[{}],"NodeAffinityPolicy":"Honor","NodeTaintsPolicy":"Ignore","PodNodeAffinity":{},"PodTolerations":[{"key":"node.kubernetes.io/not-ready","operator":"Exists","effect":"NoExecute","tolerationSeconds":300},{"key":"node.kubernetes.io/unreachable","operator":"Exists","effect":"NoExecute","tolerationSeconds":300}]}

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• :white_check_mark: login: SataQiu / name: Shida Qiu (f598b8909a59a0384cf032e337634301fb08879f)

[a7i]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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[a7i]

/lgtm

[a7i]

Thank you for your contribution @SataQiu 🏆