actor: fix example test function naming convention

This commit updates the example test function names to follow Go's
convention for example functions. The functions were renamed from
ExampleBasicActor and ExampleStructActor to Example_basicActor and
Example_structActor respectively.

This naming convention with an underscore ensures that the examples
are still recognized as valid example functions by the Go testing
framework while avoiding potential naming conflicts with actual types
in the package.

Author: Roasbeef

actor/example_basic_actor_test.go

@@ -23,9 +23,9 @@ type BasicGreetingResponse struct {
 	Greeting string
 }
 
-// ExampleBasicActor demonstrates creating a single actor, sending it a message
+// Example_basicActor demonstrates creating a single actor, sending it a message
 // directly using Ask, and then unregistering and stopping it.
-func ExampleBasicActor() {
+func Example_basicActor() {
 	system := actor.NewActorSystem()
 	defer system.Shutdown()
 

actor/example_struct_actor_test.go

@@ -68,9 +68,9 @@ func (s *StatefulCounterActor) Receive(ctx context.Context,
 	return fn.Err[CounterResponse](fmt.Errorf("invalid CounterMsg"))
 }
 
-// ExampleStructActor demonstrates creating an actor whose behavior is defined
+// Example_structActor demonstrates creating an actor whose behavior is defined
 // by a struct with methods, allowing it to maintain internal state.
-func ExampleStructActor() {
+func Example_structActor() {
 	system := actor.NewActorSystem()
 	defer system.Shutdown()