add debug counter to count `call` reusing cases.

debug_counter.h

@@ -46,6 +46,7 @@ RB_DEBUG_COUNTER(mc_miss_by_distinct)
 RB_DEBUG_COUNTER(mc_miss_by_refine)
 RB_DEBUG_COUNTER(mc_miss_by_visi)
 RB_DEBUG_COUNTER(mc_miss_spurious)
+RB_DEBUG_COUNTER(mc_miss_reuse_call)
 
 /*
  * call cache fastpath usage

vm_insnhelper.c

@@ -1458,6 +1458,7 @@ calccall(const struct rb_call_data *cd, const rb_callable_method_entry_t *me)
     }
     else {
         RB_DEBUG_COUNTER_INC(mc_miss_spurious);
+        (void)RB_DEBUG_COUNTER_INC_IF(mc_miss_reuse_call, cc->call != vm_call_general);
         return cc->call;
     }
 }