Update documentation

Clarify ability to use @MessageMapping methods on both @Controller as
well as @RestController.

Add section on configuring connections (including credentials) to the
message broker and clarify the use of the login/passcode headerers of
the STOMP CONNECT frame.

Add note on when to add the reactor-tcp dependency.

Issue: SPR-11464, SPR-11436, SPR-11449
Do not inspect meta-annotations on Java annotations

This commit introduces a new isInJavaLangAnnotationPackage(Annotation)
method in AnnotationUtils. This method is now used in AnnotationUtils,
AnnotatedElementUtils, and MetaAnnotationUtils to ensure that search
algorithms do no search for meta-annotations on annotations in the
"java.lang.annotation" package.

The following are some empirical results from this change:

- The number of times that the findAnnotation(Class,Class,Set) method in
  AnnotationUtils is recursively invoked while executing
  AnnotationUtilsTests drops from 51 to 29.

- The number of times that the process(AnnotatedElement) method in
  AnnotationUtils.AnnotationCollector is recursively invoked while
  executing AnnotationUtilsTests.getRepeatableFromMethod() drops
  from 16 to 2.

- The number of times that the doProcess() method in
  AnnotatedElementUtils is recursively invoked while executing the
  "getAnnotationAttributes() On MetaCycleAnnotatedClass with missing
  target meta-annotation" test in AnnotatedElementUtilsTests drops
  from 23 to 5.

- The number of times that the findAnnotationDescriptor(Class,Set,Class)
  method in MetaAnnotationUtils is recursively invoked while executing
  the "findAnnotationDescriptor() on MetaCycleAnnotatedClass with
  missing target meta-annotation" test in MetaAnnotationUtilsTests drops
  from 16 to 8.

Issue: SPR-11483