Applies the updated NodeVersion object with one request
instead of two. This makes sure that the first request does
not accidentially put the cluster into a "updgrade in progress"
status. Which would lead users to having to run apply twice.
* `upgrade apply` will try to make the locally configured and
actual version in the cluster match by appling necessary
upgrades.
* Skip image or kubernetes upgrades if one is already
in progress.
* Skip downgrades/equal-as-running versions
* Move NodeVersionResourceName constant from operators
to internal as its needed in the CLI.
* introduce handleImageUpgrade & handleServiceUpgrade
* rename cloudUpgrader.Upgrade to UpgradeImage
* remove helm flag
* remove hint about development status
