Prior to this commit, the findAllLocalMergedAnnotations() method in
AnnotationDescriptor altered between the use of TYPE_HIERARCHY and
TYPE_HIERARCHY_AND_ENCLOSING_CLASSES for the SearchStrategy, depending
on @NestedTestConfiguration semantics; however, when searching for
"local" annotations, there is no need to search the enclosing class
hierarchy since AnnotationDescriptor#next() handles that use case.
This commit therefore switches to using only the TYPE_HIERARCHY
strategy.
This commit also discontinues the use of
MergedAnnotationCollectors.toAnnotationSet() in order to avoid the
unnecessary creation of a temporary List when collecting synthesized
annotations in a LinkedHashSet.
Closes gh-25985
68934f1b79