Add appversion to Chart.yaml and renovate

Adding appversion to Chart.yaml allows us to use helm list to see the application that is installed. For BBCTL, we will likely be pulling from the appversion field for some commands.

In Chart.yaml, appversion should be kept in sync with the version of the image being pulled. Have renovate automatically check and update appversion against the image version.

Example: https://repo1.dso.mil/platform-one/big-bang/apps/developer-tools/gitlab/-/blob/main/renovate.json#L18-25