B-physics migration of combined dielectron+muon chains, e.g. 'HLT_e9_lhvloose_e5_lhvloose_bBeeM6000_mu4_L1BPH-0M9-EM7-EM5_MU6' (ATR-23839)

• TrigMultiTrkComboHypo is adopted to look for close-by electrons originated from the same EM cluster (chains with 'L1BPH-0DR3-EM7J15')
• combined dielectron+muon are added to LS2_v1 menu, but we are still waiting for ATR-23965; hack of the auto-generated IMEmptyMuonSeq1_Electron can be used in the meantime (add ~lyubushk/public/Trigger/fixIMEmptySeq_bBeeM6000.py to --postInclude option, see ~lyubushk/public/Trigger/test_bBeeM6000.sh for example);
• add more options for Bmumux decays of B_c+ and fix some bugs;
• add entry for di-electron chains in EDM;
• some improvements in the coding style are taken from !44579 (closed)

CC: @abarton