feat(core): Add minor fast optimization for context visitor

Author: PerfectSlayer

dd-trace-core/src/main/java/datadog/trace/core/propagation/TracingPropagator.java

@@ -63,6 +63,9 @@ public <C> Context extract(Context context, C carrier, CarrierVisitor<C> visitor
 
   private static <C> AgentPropagation.ContextVisitor<C> toContextVisitor(
       CarrierVisitor<C> visitor) {
+    if (visitor instanceof AgentPropagation.ContextVisitor) {
+      return (AgentPropagation.ContextVisitor<C>) visitor;
+    }
     return (carrier1, classifier) -> visitor.forEachKeyValue(carrier1, classifier::accept);
   }
 }