Use CheCluster v2alpha1 as devworkspace che configuration

[metlos]

We need to use conversion webhooks and start storing a v2alpha1 version of the CheCluster that would have the old che7 configuration stashed under spec.che7 and devworkspace config properties directly under spec. This way, the che operator and devworkspace che operator could react to this new version and one would just read the spec from under che7 and continue normally as we do at the moment and the other would read the dw configuration and apply it to devworkspaces.

Disallowing more instances of CheCluster is a matter of checking the cluster state during reconciliation.

This needs to be implemented in the following order:

• Define v2alpha1 of CheCluster (Define CheCluster v2alpha1 #19449)
• Start using CheCluster v2alpha1 in DWCO (Start using CheCluster v2alpha1 in DWCO #19450)
• Implement a conversion webhook to convert CheCluster v1 into CheCluster v2alpha1 (Implement a conversion webhook from CheCluster v1 to v2alpha1 #19451)
• Start handling CheCluster v2alpha1 in the che-operator (Start handling CheCluster v2alpha1 in the che-operator #19453)
• Use v2alpha1 as the storage version of CheCluster

[metlos]

This is superseded by #19845. Once we get to the point where we need to define the new CR version, we can revisit this issue or create a new one.