CollectAvailableImages finds all the known image metadata for containers in the controllers given.

PrintResults outputs a result set to the `io.Writer` provided, at the given level of verbosity: - 2 = include skipped and ignored resources - 1 = include skipped resources, exclude ignored resources - 0 = exclude skipped and ignored resources.

How did this update get triggered?.

NB: these get sent from fluxctl, so we have to maintain the json format of this.

A tagged union for all (both) kinds of update.

ImageSpec is an ImageID, or "<all latest>" (update all containers to the latest available).

ReleaseKind says whether a release is to be planned only, or planned then executed.