Update LCG generators layer to LHCB_8

This is needed to be able to build with LCG 106c

added lhcb-gaudi-head lhcb-head labels

mentioned in merge request lhcb-core/LHCbNightlyConf!1333 (merged)

• [2025-03-14 01:04] Validation started with lhcb-gaudi-head#4170
• [2025-03-14 01:05] Validation started with lhcb-head#4131
• [2025-03-14 12:52] Validation started with lhcb-gaudi-head#4171
• [2025-03-15 01:02] Validation started with lhcb-gaudi-head#4172
• [2025-03-15 01:02] Validation started with lhcb-head#4132
• [2025-03-16 01:02] Validation started with lhcb-gaudi-head#4173
• [2025-03-16 01:03] Validation started with lhcb-head#4133
• [2025-03-17 01:03] Validation started with lhcb-gaudi-head#4174
• [2025-03-17 01:03] Validation started with lhcb-head#4134

@gcorti @clemenci @mimazure Could I get an approval here? Needed for LCG106 migration.

added Generators new feature labels

removed lhcb-gaudi-head label

removed lhcb-head label

approved this merge request

merged

mentioned in commit caf23184

Compatible with LCG_105c