Migrate all catalog functions to fn.WithDocs for --help/--doc support

[efiacor]

Context

PR kptdev/krm-functions-sdk#752 adds fn.WithDocs to the SDK, enabling --help and --doc support via //go:embed. This issue tracks migrating all catalog functions to use it.

Parent issue: #4485

Already using fn.AsMain (just need fn.WithDocs added)

These 8 functions already use fn.AsMain — migration is adding //go:embed + fn.WithDocs and deleting generated/docs.go:

• set-labels
• set-namespace
• set-image
• delete-annotations
• apply-replacements
• render-helm-chart
• starlark
• kubeconform

Still using kyaml/fn/framework + command.Build (full migration needed)

These functions need rewriting from framework.ResourceList to fn.ResourceList:

Simple (thin wrappers)

• sleep
• remove-local-config-resources
• set-enforcement-action
• upsert-resource

Medium

• apply-setters
• create-setters
• list-setters
• search-replace
• annotate-apply-time-mutations

Complex

• set-annotations
• ensure-name-substring
• gatekeeper
• generate-kpt-pkg-docs (blocked on list-setters)

Migration steps per function

1. Add //go:embed README.md and //go:embed metadata.yaml
2. Pass fn.WithDocs(readme, metadata) to fn.AsMain
3. Delete generated/docs.go
4. For legacy functions: rewrite from framework.ResourceList to fn.ResourceList / fn.Runner
5. Verify kpt fn doc works: docker run --rm <image> --help

Done when

All catalog functions support --help and --doc via the SDK, and generated/docs.go files are removed.