[MCH] add cut random fraction setting for the cases with and without ITS

Two new environment variables are introduced to provide the fraction of
rejected MCH events separately for the cases where ITS is either included
(CUT_RANDOM_FRACTION_MCH_WITH_ITS) or excluded (CUT_RANDOM_FRACTION_MCH_NO_ITS)
from the data taking.

The CUT_RANDOM_FRACTION_MCH variable, as well as the two new ones, can still
be overridden by setting them explicitly in the shell environment,
therefore the changes are backward compatible.

Author: aferrero2707

DATA/production/workflow-multiplicities.sh

@@ -252,7 +252,21 @@ elif [[ $BEAMTYPE == "PbPb" ]]; then
 else
   : ${CUT_RANDOM_FRACTION_ITS:=0.95}
 fi
-[[ $RUNTYPE != "COSMICS" ]] && : ${CUT_RANDOM_FRACTION_MCH:=0.7}
+
+# Random data sampling fraction for MCH
+if [[ $BEAMTYPE == "pp" ]]; then
+    : ${CUT_RANDOM_FRACTION_MCH_WITH_ITS:=0.5}
+    : ${CUT_RANDOM_FRACTION_MCH_NO_ITS:=0.995}
+elif [[ "$HIGH_RATE_PP" == "1" ]]; then
+    : ${CUT_RANDOM_FRACTION_MCH_WITH_ITS:=0.7}
+    : ${CUT_RANDOM_FRACTION_MCH_NO_ITS:=0.995}
+elif [[ $BEAMTYPE == "PbPb" ]]; then
+    : ${CUT_RANDOM_FRACTION_MCH_WITH_ITS:=0.9}
+    : ${CUT_RANDOM_FRACTION_MCH_NO_ITS:=0.995}
+else
+    : ${CUT_RANDOM_FRACTION_MCH_WITH_ITS:=0.99}
+    : ${CUT_RANDOM_FRACTION_MCH_NO_ITS:=0.99}
+fi
 
 #if [[ "$HIGH_RATE_PP" == "1" ]]; then
   # Extra settings for HIGH_RATE_PP