Improve TTree::Print("clusters") output.
Improve TTree::Print("clusters") output.

Add actual number of cluster included in a Range.

Fix ROOT-10594

root-mirror/root,karies/root,root-mirror/root,karies/root,root-mirror/root,root-mirror/root,root-mirror/root,root-mirror/root,olifre/root,olifre/root,olifre/root,root-mirror/root,olifre/root,olifre/root,karies/root,karies/root,karies/root,root-mirror/root,karies/root,root-mirror/root,olifre/root,olifre/root,root-mirror/root,olifre/root,olifre/root,karies/root,olifre/root,root-mirror/root,karies/root,karies/root,karies/root,olifre/root,karies/root