- Remove the need for upfront_decoder.bind( source = ... ): compute the relevant argument from the requested location in _get_unpacked and pass it explicitly
- Remove ability to pack using deprecated, old-style 32-bit references which are known to overflow and lead to data corruption - only keep the ability to pack 64-bit references. Throw an exception if such an packing version still requested (note: the unpacking is left as-is)
- Improve implementation of packing and unpacking of references
- Unify setters in event model classes for SmartRef and pointer: remove redundant overloads (which could be ambiguous, and require additional casts!)

- use this as a base class of ExtendedPrimaryVertex, the class stored by
  PrimaryVertexContainer
- introduce old--style packers/unpackers for PrimaryVertex
- added constexpr to propertyName of old-style packers
- added packing_mapping for soatype packers

- streamlined PV unbiasing code
- updated Particle packing checker

- add code to support Tagger::TagResult as strong enum
- getters return enum instead of short int
- setters require enum instead of short int

and make `unpack` return a StatusCode to know when an unpacker has
failed, in which case, if available, another unpacker for the same
CLID can be tried