Add "Start invocation" in InvocationStateMachine, symmetric with "End invocation" log line

Author: slinkydeveloper

sdk-core/src/main/java/dev/restate/sdk/core/InvocationStateMachine.java

@@ -200,6 +200,7 @@ void onStartMessage(MessageLite msg) {
       span.addEvent(
           "Start", Attributes.of(Tracing.RESTATE_INVOCATION_ID, startMessage.getDebugId()));
     }
+    LOG.info("Start invocation");
 
     // Execute state transition
     this.transitionState(InvocationState.REPLAYING);

sdk-core/src/main/java/dev/restate/sdk/core/ResolvedEndpointHandlerImpl.java

@@ -50,7 +50,7 @@ public InvocationFlow.InvocationOutputPublisher output() {
 
   @Override
   public void start() {
-    LOG.info("Start processing invocation");
+    LOG.trace("Start processing invocation");
     stateMachine.startAndConsumeInput(
         SyscallCallback.of(
             request -> {