I am running Rancher on RKE2 in an airgapped environment and have numerous downstream RKE2 clusters (also airgapped, and built using Rancher). I am working on upgrading the Rancher server from v2.7.x to v2.8.x including RKE2 it's running on. My question is, once Rancher is upgraded to 2.8.x using images from my private registry, will I be able to upgrade my downstream RKE2 clusters to the supported RKE2 versions using the Rancher console, without the need for any additional images or binaries? Are all artefacts needed for downstream cluster upgrades included in the Rancher build?