Significant drop in throughput (6.5%) due to !874 should be investigated

See discussion !874 (comment 5863844)

Moore HLT1 throughput (Moore_hlt1_pp_default test):

• before Rec!2958 (merged) -> 28484.5 Events/s
• first implementation of new VELO decoding -> 25072.6 Events/s (-12.11%)
• adding reserve statements -> 26573.5 Events/s (-6.53%)
• removing allocation of new RawEvent and event local allocator -> 26828.5 Events/s (-5.81%)