Rename @TransientAuthentication to @Transient

It is quite likely we will need to prevent certain Exceptions from being
saved or from triggering a saved request. When we add support for this,
we can now leverage @Transient vs creating a new annotation.

Issue: gh-5481

core/src/main/java/org/springframework/security/core/Transient.java

@@ -34,5 +34,5 @@ import java.lang.annotation.Target;
 @Retention(RetentionPolicy.RUNTIME)
 @Inherited
 @Documented
-public @interface TransientAuthentication {
+public @interface Transient {
 }