[AA] Add stub annotationApplicableTargets extension.

Introduce an extension method to retrieve the set of applicable targets
for an annotation, given the annotation class's symbol.

This extension on `KtSymbolInfoProvider` causes a large amount of churn
in test data files, so this change starts off by introducing the
property and always making it return null. A future change will
introduce the actual behavior change, and will include the testdata
changes for the few tests that actually return useful data for this
property.

analysis/analysis-api/testData/symbols/symbolByReference/javaClassWithEmptyAnnotationName.txt

@@ -22,4 +22,5 @@ KtNamedClassOrObjectSymbol:
   typeParameters: []
   visibility: Public
   getContainingModule: KtSourceModule "Sources of main"
+  annotationApplicableTargets: null
   deprecationStatus: null