fix: avoid mutating metric families during write

[bhope]

What this PR does / why we need it:

Fixes a bug where metric family types could be mutated across requests when serving different content types.

When serving Prometheus text output, info and stateset metrics were rewritten to gauge by mutating shared metric families. This caused subsequent OpenMetrics requests to return incorrect types. This change ensures per-request sanitization does not affect stored metrics.

How does this change affect the cardinality of KSM:
Does not change cardinality.

Which issue(s) this PR fixes:
Fixes #2805

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: bhope
Once this PR has been reviewed and has the lgtm label, please assign mrueg for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[k8s-ci-robot]

This issue is currently awaiting triage.

If kube-state-metrics contributors determine this is a relevant issue, they will accept it by applying the triage/accepted label and provide further guidance.

The triage/accepted label can be added by org members by writing /triage accepted in a comment.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[bhope]

@mrueg @rexagod this PR is waiting on workflow approval (CI hasn’t started yet). When you have a moment, could you approve the workflow so checks can run? Happy to get a review once CI is green. Thanks!

[bhope]

All CI checks have passed now. Thanks.