Make CaloClusterizationTool const

We are starting the work on the calo software for the upgrade. As a first step, we want to have a running version of the code which is thread safe with the minimal changes.

This MR changes the CaloClusterizationTool to make it const and propagates the changes to the users: CellularAutomatonAlg and L0Calo2CaloTool (this last one is not used in the offline reconstruction and might be removed in a future round, but for now we keep it since we prefer to apply changes one by one). Also the interface of the CaloClusterizationTool has been updated accordingly, so MR LHCb!1295 (merged) is needed together with this one to be able to compile.

As for testing (even though the changes are minimal), since we don't yet have a running version in MiniBrunel I have run on 200 upgrade events from Brunel and checked the number of Ecal clusters and iterations to achieve them is the same after our changes.

Finally, we know there are many parts of the code to improve but as said for now we just want to have a thread-safe running version of the Calo Reco. Any comment/suggestion on that side would be appreciated!