New B to Ks h h h model in EvtGenExtras for master

cherry pick MR !528 (merged) for 'Sim09' into 'master' and fix conflicts

Closes LHCB-1857

It consists of commits:

• eccb58d0
• 7f15b9b0
• 9f1d6e92
• a12d6587
• 3f9103db
• 74a1ec59