Try to create an EventContext aware ShallowCopy method, that also returns unique_ptr.

Add a EventContext aware ShallowCopy function that also returns smart pointers.

The function should be callable in AnalysisBase e.g with the result of currentContext() as second arguement.

But we have to ignore the ctx in `AnalysisBase as

• there is not real class for it in
• we can never dereference/use the return of currentContext()
• There is not DataLink ctor accepting it Here (void) seemed to avoid a bit fancy pre-processor indentation

Mentioning

• @dguest who wanted something like this
• @krumnack who clarified to me that the current idiom in AnalysisBase is to pass EventContext the return of currentContext() by reference and then ignore it at the bottom of the call chain.
• And @akraszna , @ssnyder who probably should OK this