chore(mgmt): remove obsolete PKO cleanup tooling (AROSLSRE-1197)

[raelga]

AROSLSRE-1197

What

Removes the obsolete one-time PKO (Package Operator) cleanup tooling from the management cluster rollout:

• Drops the cleanup-pko EV2 Shell step (and its TODO) from dev-infrastructure/mgmt-pipeline.yaml.
• Drops the cleanup-pko build block from the pipeline buildStep (the recreate-system-pool / recreate-broken-pools builds are untouched).
• Deletes the dev-infrastructure/scripts/cleanup-pko-resources/ Go module.
• Removes its go.work entry and the .gitignore binary entry.

Why

The cleanup-pko step and its Go helper were a one-time migration to remove orphaned PKO resources that blocked cluster deletion on MGMT clusters (epic AROSLSRE-782). #5366 hardened it to run as a built Go binary. The step itself carried a TODO: Remove this PKO cleanup step once all management clusters have been cleaned up ([ARO-23308](https://redhat.atlassian.net/browse/ARO-23308)).

Now that the rollout has completed across all management clusters, the step runs on every mgmt rollout as dead code. This removes it.

Testing

• make validate-changed-config-pipelines passes.
• go work sync clean; no module references the deleted path.
• grep -r cleanup-pko returns no matches after the change.

Special notes for your reviewer

Warning

/hold — do not merge until we have validation that the PKO cleanup has actually completed on all management clusters (int/stage/prod). Removing the step early would strand orphaned PKO resources on any cluster that has not yet been swept. Lift the hold once that is confirmed.

The unrelated package-operator library dependency used by tooling/olm-bundle-repkg is intentionally untouched.

PR Checklist

• PR is scoped to a single task (no mixed concerns)
• Title follows Conventional Commits format
• Summary explains the "Why" behind the change
• Linked to relevant ticket/issue
• Screenshots included (if graph/UI/metrics changes)
• Self-reviewed the diff
• CI/CD checks are passing (ignore Tide)
• Draft PR used for WIP (if applicable)
• Commit history is clean (rebased/squashed)
• Tricky code blocks are commented
• Specific reviewers tagged
• All comment threads resolved before merge

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: raelga

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[raelga]

/hold

Holding until we have validation that the PKO cleanup has completed on all management clusters (int/stage/prod). Removing the rollout step before that is confirmed would strand orphaned PKO resources on any cluster not yet swept. /hold cancel once confirmed.

[Copilot]

Pull request overview

Removes the now-obsolete “cleanup-pko” management cluster rollout step and its associated one-off Go tooling, reducing dead code in the mgmt EV2 pipeline and workspace module list.

Changes:

• Removed the cleanup-pko EV2 Shell step and its build output generation from dev-infrastructure/mgmt-pipeline.yaml.
• Deleted the dev-infrastructure/scripts/cleanup-pko-resources/ Go module (code + tests + go.mod/go.sum).
• Removed related workspace and ignore-list entries (go.work, dev-infrastructure/.gitignore).

Reviewed changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
go.work	Removes the deleted PKO cleanup module from the Go workspace.
dev-infrastructure/mgmt-pipeline.yaml	Drops the PKO cleanup binary build and the rollout step that executed it.
dev-infrastructure/.gitignore	Removes the ignored PKO cleanup binary path since it no longer exists.
dev-infrastructure/scripts/cleanup-pko-resources/main.go	Deletes the obsolete PKO cleanup implementation.
dev-infrastructure/scripts/cleanup-pko-resources/main_test.go	Deletes tests for the removed PKO cleanup tool.
dev-infrastructure/scripts/cleanup-pko-resources/go.mod	Deletes the standalone module definition for the removed tool.
dev-infrastructure/scripts/cleanup-pko-resources/go.sum	Deletes dependency checksums for the removed module.