Add the ability to append to the result json file for wallclock benchmarks (AI Generated)

Author: OsamaAhmad00

core/src/walltime.cpp

@@ -184,21 +184,25 @@ static void append_codspeed_benchmarks_to_json(
       continue;
     }
 
+    // State 0: Find the outer root object closure '}'
     if (state == 0 && ch == '}') {
       state = 1;
       continue;
     }
 
+    // State 1: Find the array list closure ']'
     if (state == 1 && ch == ']') {
       state = 2;
+      // Truncate right here! This preserves whatever character came right before the array bracket ']'
+      truncation_pos = pos;
       continue;
     }
 
+    // State 2: Check what the last character inside the array was
     if (state == 2) {
       if (ch == '[') {
         array_was_empty = true;
       }
-      truncation_pos = pos + std::streamoff(1);
       break;
     }
   }