WIP: ChargedProtoANNPID: replace inheritance from Input by type-erasure

Gerhard Ravenrequested to merge
master-ChargedProtoANNPID-std-function into master

Change 'Input' from an abstract base class to a type-erased 'handle'. This enables the use of value semantics (instead of owning pointers), simplifying the code, and making it less work to extend it.

In addition, some modernization changes as side-effect...

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