[DOCS] Upgrade runbook for every install path #3693

docs/guides/upgrade.md covers only ate-setup. Rewrite it for every install path, following the version skew policy's upgrade order.

Tracks "Rewrite the upgrade runbook for every install path" in the Operator Supplied Values workstream of the Extensible Install Roadmap.

Required changes

• kustomize: apply the release stage bases ([FEATURE] Generate the release layout from ate-setup render #3678); sizing patches stay in the operator's kustomization.
• Helm: upgrade the stage charts with the operator's values ([FEATURE] Generate per-stage Helm charts and an install chart from the rendered release #3682).
• ate-setup: the record carries Components and settings ([FEATURE] ate-setup install record merges partial deploys and stores Components #3688).
• Each path runs the drift report ([FEATURE] ate-setup reports out-of-band changes before overwriting them #3689) first.

Dependencies: #3678, #3688, #3689. Helm section after #3682.

Enforcement: the runbook commands match the commands the upgrade CI jobs run (#3679, #3687, #3694).

Parent Issue: #3165