[Docs]: Add Multi Operand version support in Operator RNs

• Eng JIRA https://issues.redhat.com/browse/JDG-4287 
• PR https://github.com/infinispan/infinispan-operator/pull/1545 
• Doc https://issues.redhat.com/browse/JDG-5335 

From now, you can have a single {ispn_operator} version that supports multiple versions of {brandname}. This means that you can have multiple clusters with different {brandname} versions in separate namespaces and upgrade between supported versions. Moreover, you can roll back a failed Hot Rod rolling upgrade to the previous version if the original cluster is still present.

NOTE: TBD Specify which {brandname} versions will be supported by the 8.4 Operator.