Modernize HltPackedData{Writer,Decoder}
- make HltPackedDataDecoder thread safe
- make HltPackedDataWriter a Gaudi::Functional::MergingConsumer (keeping the explicit datahandle to update RawEvent)
- move code and data common to Writer and Decoder into HltPackedData.h
- amalgamate decoder and writer headers into their .cpp files
- prefer std::string_view over const std::string&
- make all StandardPacker methods static
- introduce some namespaces
requires Moore!949 (merged)
Edited by Gerhard Raven