Charm HLT2 lines: Xic0 to pk

Prototype of Xic0 to pk lines.

Following lines are defined:
1. prompt lines:
[Xi_c0 -> p+ K-]CC
[Omega_c0 -> p+ K-]CC

2. b-decays:
[Xi_b- -> (Xi_c0 -> p+ K-) pi-]CC
[Omega_b- -> (Omega_c0 -> p+ K-) K-]CC

Current efficiencies based on hlt1_filtered_minbias

| Line | Events / passed | Efficiency | Rate |
| Hlt2Charm_Omegac0ToPpKm_Line |  #=14983 Sum=1 |  Eff=|(0.006674231 +- 0.00667401)% |  Rate ~ 67 Hz |
| Hlt2Charm_Xic0ToPpKm_Line |  #=14983 Sum=3 |  Eff=|(0.02002269 +- 0.0115589)%|  Rate ~ 200 Hz |
| Hlt2Charm_XibmToXic0Pim_Xic0ToPpKm_Line |  #=14983 Sum=0 |  Eff=( 0.000000 +- 0.00000 )% |  Rate ~ 0.0 Hz |
| Hlt2Charm_Omegac0ToPpKm_Line |  #=14983 Sum=0 |  Eff=( 0.000000 +- 0.00000 )% |  Rate ~ 0.0 Hz |

Run 2 stripping: https://gitlab.cern.ch/lhcb/Stripping/-/blob/2018-patches/Phys/StrippingSelections/python/StrippingSelections/StrippingCharm/StrippingNeutralCBaryons.py

TO DO:

• tune selection

added Charm RTA hlt2 selection labels

assigned to @msaur

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• f0e0f514 - fix

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• dd1be348 - b-decay lines added
• d5e4c70a - added ghostprob cut

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• 019cccfa - cuts based on Run2 stripping
• 804b0e67 - ix

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requested review from @lpica and @roneil

requested review from @fsouzade, @jingyi, @mstahl, and @tpajero

@lpica @roneil @fsouzade @jingyi @tpajero This MR is based on existing Run2 stripping + newly added lines from b-decays.

Currently the rates are still too high, so if you would have any ideas how to improve selection that would be great.

added 2 commits

• fb022a44 - tighter proton PID cuts, looser dira and
• d7a6d89d - tighter proton PID cuts, looser dira and

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• 45c5d2bd - tightening PID_P - PID_K conditions to decrease rate

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• 2c0dd0cc - removed track chi2 and ghostprob cuts

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