Support SGShardedCluster on the web console

With the introduction of the SGShardedCluster, we must now provide support to this CRD on the web console.

Documentation for the specs on this new CRD can be found here: https://stackgres.io/doc/1.5/reference/crd/sgshardedcluster/

Apart from some minor variations, most of them are based on the SGCluster, so ideally, there should be a way to reuse the code used on the SGCluster, at least on the web console forms which are quite complex and have been heavily customized.

More info on SGShardedCluster can be found on #2227 (closed) and #2250 (closed)