Migrate various Hlt rawbank decoders to Gaudi::Functional
Migrate HltDecReportsDecoder, HltSelReportsDecoder, HltTrackReportsDecoder and HltVertexReportsDecoder.
HltPackedDataDecoder is not migrated yet, as it looks like the best migration is to split it into one decoder 'per type' and use a 'SuperAlgorithm' to package them as a single decoder...