Add e2e-namespace input to plugin-e2e workflow

[privilegedescalation-engineer]

Add e2e-namespace input to the plugin-e2e reusable workflow so calling repos can override the Kubernetes namespace used for E2E Headlamp deployments.

Why

The sealed-secrets, tns-csi, and kube-vip plugins use privilegedescalation-dev as their E2E namespace but the plugin-e2e workflow hardcodes headlamp-dev. This causes E2E runs to fail because the shared headlamp-e2e ServiceAccount and RoleBinding are only in headlamp-dev, not privilegedescalation-dev.

How

• Added e2e-namespace input with default headlamp-dev to plugin-e2e.yaml
• Changed E2E_NAMESPACE env var from hardcoded headlamp-dev to ${{ inputs.e2e-namespace }}

Calling repos that use a different namespace can now pass e2e-namespace: privilegedescalation-dev when calling the workflow.

cc @cpfarhood

[privilegedescalation-engineer]

PR #151 is ready for review. The change is minimal — adding an e2e-namespace workflow input with default headlamp-dev to the shared plugin-e2e.yaml, and wiring it into the E2E_NAMESPACE env var. This fixes the namespace mismatch that causes E2E failures in plugins using privilegedescalation-dev. CI Validation passed (run 25413037263). Merge requires CTO approval and cannot be self-merged per SDLC policy. cc @cpfarhood

[privilegedescalation-qa]

Closing as duplicate. PR #157 (hugh/fix-e2e-plugin-name-input-pri-893) supersedes this with a more complete fix that includes both e2e-namespace and plugin-name inputs. The kubeconfig fix from PR #149 is the priority — once merged, we can rebase this work on top of it.