Add a2(1230) exotic resonance candidate (#1803)

(cherry picked from commit a8e801a)

Author: BongHwi

MC/config/PWGLF/ini/tests/GeneratorLF_Resonances_pp_exotic.C

@@ -13,6 +13,7 @@ int External()
         20223,   // f_1(1285)
         20333,   // f_1(1420)
         335,     // f_2(1525)
+        115,     // a_2(1230)
         10323,   // K1(1270)+
         -10323,  // K1(1270)-bar
         123314,  // Xi(1820)-
@@ -28,6 +29,7 @@ int External()
         {310, -321, 211}, // f_1(1285)
         {310, -321, 211}, // f_1(1420)
         {310, 310},       // f_2(1525)
+        {310, 310},      // a_2(1230)
         {321, 211},       // K1(1270)+
         {-321, -211},     // K1(1270)-bar
         {2212, 211},      // Delta(1232)+

MC/config/PWGLF/pythia8/generator/resonancelistgun_exotic.json

@@ -62,6 +62,15 @@
         "etaMax": 1.2,
         "genDecayed": true
     },
+    "a_2(1230)" : {
+        "pdg": 115,
+        "n": 1,
+        "ptMin": 0.0,
+        "ptMax": 20,
+        "etaMin": -1.2,
+        "etaMax": 1.2,
+        "genDecayed": true
+    },
     "K1(1270)+": {
         "pdg": 10323,
         "n": 1,

MC/config/PWGLF/pythia8/generator/resonancelistgun_exotic_pbpb.json

@@ -62,6 +62,15 @@
         "etaMax": 1.2,
         "genDecayed": true
     },
+    "a_2(1230)" : {
+        "pdg": 115,
+        "n": 1,
+        "ptMin": 0.0,
+        "ptMax": 20,
+        "etaMin": -1.2,
+        "etaMax": 1.2,
+        "genDecayed": true
+    },
     "K1(1270)+": {
         "pdg": 10323,
         "n": 10,