feat: Add pod-free wait-for-delete resource action. Fixes #15874

[AndreKurait]

Fixes #15874

Motivation

There is currently no clean way to block a workflow until a Kubernetes resource is fully deleted without creating a pod. Users resort to script templates running kubectl wait --for=delete in a loop, which incurs pod scheduling, image pull, and memory overhead for what is fundamentally a single API call.

This adds a new pod-free action: wait with waitFor: delete for resource templates, following the same controller-side pattern used by Suspend nodes.

Modifications

• API (workflow_types.go): Added wait to the Action enum and a new WaitFor field (enum: delete) on ResourceTemplate.
• Validation (validate.go): waitFor is required when action: wait, forbidden otherwise. successCondition, failureCondition, and outputs are disallowed with wait.
• Controller (operator.go): executeResource intercepts action: wait before pod creation. checkResourceWaitForDelete uses the dynamic client to check resource existence — 404 means succeeded, exists means requeue. podReconciliation skips wait-action nodes so they are not flagged as pod-missing.
• Controller (controller.go): Added a restMapper to resolve GVK → GVR for the dynamic client GET.
• CRDs/OpenAPI: Regenerated via controller-gen and openapi-gen.

Verification

• Unit tests (operator_test.go): Two test cases — resource already deleted (→ Succeeded), resource still exists (→ Running, no pod created).
• Unit tests (validate_test.go): Five test cases covering valid usage and all invalid combinations (missing waitFor, waitFor on non-wait action, with successCondition, with outputs).
• Existing test regression: Updated TestInvalidResourceWorkflow expected error message to include wait in the valid actions list. Full workflow/controller (82s) and workflow/validate test suites pass.
• E2E test (resource_template_test.go): TestWaitForDeleteAlreadyGone — submits a workflow that waits for a non-existent ConfigMap, expects immediate success.
• Lint: golangci-lint v2.11.3 passes with 0 issues. go vet clean. Feature doc validated.

Documentation

• docs/resource-template.md: Added "Wait for Resource Deletion" section with usage example.
• .features/pending/wait-for-delete-resource-action.md: Feature description file for release notes.
• The waitFor enum is designed for future extension (e.g. waitFor: condition) without breaking changes.