CaloRec: Add option to create trigger decorations to Cluster Maker

This MR adds an option to the offline CaloClusterMaker that allows it to create the additional decoration that TrigCaloClusterMaker adds to the cluster collection, which simply contains the number of cells in every cluster. If the option to create the additional decoration is not set, there are no changes to the behaviour of the code.

(This is how the CaloGPUHybridClusterProcessor from CaloRecGPU already works.)

This would be the first step on the road to potentially retiring TrigCaloClusterMaker, which (apart from this decoration and the monitoring) is essentially redundant given that it reimplements the functionality of the offline cluster maker. Ultimately, this will allow us to greatly reduce code duplication between the online and offline and simplify our configuration, and for the trigger in particular it will allow us to better decouple the cluster monitoring from the actual cluster making algorithm, which goes hand in hand with other changes that are being considered for it.