Add basic PbPb sequence

This MR defines a new sequence hlt1_PbPb_veloSP. This sequence performs VELO, PV, and ECAL reconstruction with no GEC. The MR also introduces a heavy ion line that selects events based on total ECAL energy, number of VELO tracks, and number of PVs. Events are also selected based on whether these tracks and PVs originate from the pp or SMOG regions. This selection can be configured to handle all of the PbPb and Pb-SMOG trigger lines. The sequence runs with a throughput of about 12 kHz on a RTX 3090.

Remaining to-dos include:

• Create remaining PbPb and Pb-SMOG trigger lines
• PV reconstruction has been modified to not crash on large events. This should be fixed in a more robust way.
• Resize slice fragments to prevent Allen from hanging on large events
• Calculate total ECAL energy
• An ECAL-based lumi line should be implemented. The total ECAL energy for each event should also be saved so it can be used for centrality determination.
• Add a PbPb CI test

FYI @chwong

Also FYI @dcraik, as this concerns lumi lines and possibly monitoring.