Projects: Update all projects except AthAnalysis to LCG_102b_ATLAS_6

Update all Projects except AthAnalysis (and AnalysisBase) to LCG_102b_ATLAS_6.

• The new HepMC3 layer LCG_102b_ATLAS_5 that is used in parallel fixes a build/linking issue with EvtGen as discussed in https://sft.its.cern.ch/jira/browse/SPI-2254 and AGENE-2163
• Additional updates as discussed in https://sft.its.cern.ch/jira/browse/SPI-2240:
  • Rivet 3.1.7 + YODA 1.9.7
  • MG 3.4.1,
  • Sherpa 2.2.13
  • Pythia 8.308
  • LHAPDF 6.5.3

Tagging @nstyles, @jcatmore, @ewelina

Keeping the MR in draft status until RPMs are actually available as mentioned in the last comments in https://sft.its.cern.ch/jira/browse/SPI-2254