Remove iteration over all clusters in workloads/apps/services

[nrfox]

What do you want to improve?

Handling of multicluster cluster and namespace checks.

What is the current behavior?

In the business services for workloads/services/apps, Kiali iterates over all clusters and will try to get the cluster namespace depending on whether or not Kiali is a multicluster deployment. This was only added because #5932 has not been resolved and previously requests were made to the backend per namespace. Now with #7076 work they are being made per cluster.

What is the new behavior?

Until #5932 is resolved and the frontend can disambiguate between two namespaces named the same thing on two different clusters, Kiali should instead perform a namespace check if the namespace is passed, otherwise filter out results for inaccessible namespaces. When #5932 is resolved, Kiali can do a namespace check per requested namespace.

[hhovsepy]

Seems can be done having in mind already in progress another issue: #4832

[nrfox]

Yes it can be part of or a followup to that work.