Add PropertyDescriptor.backingField/delegateField to store annotations
on the field directly in an otherwise almost empty descriptor instance,
instead of storing them with use-sites in the corresponding property
descriptor. Instead of AnnotationWithTarget, create AnnotationDescriptor
instances in AnnotationSplitter. Change DescriptorRenderer to render
annotations on "related" declarations when needed, with the explicit
use-site target if applicable.
Most changes in diagnostic test data are related to the fact that
annotations which are known to have an incompatible use-site to the
declaration they're applied at (such as `@param:`-annotation on a
function), are now not loaded at all. It's fine because the code is
erroneous, so it doesn't really matter how do we load annotations with
invalid targets (some of this logic is also changed freely in subsequent
commits). Some changes are also explained by the fact that for example
an annotation on the property which is only applicable to FIELD is now
rendered with an explicit use-site target `@field:`, regardless of
whether it did have that use-site target syntactically or not.
Basically, after this change there's no point in calling
Annotations.getUseSiteTargetedAnnotations/getAllAnnotations anymore
because it's easier and more intuitive to just use Annotations of the
corresponding descriptor -- the backing / delegate field (introduced in
this commit) or the extension receiver / setter parameter (related
behavior was fixed in previous commits). Usages of
use-site-target-related methods will be refactored out in subsequent
commits
Victor Petukhov