Unused symbol suppression: get annotation descriptors via entries

Otherwise we miss use-site targeted annotations,
and getUseSiteTargetedAnnotations does not help
So #KT-20332 Fixed

idea/testData/inspections/unusedSymbol/property/unusedButEntryPointAnnotated.kt

@@ -3,4 +3,10 @@ val entryPoint = ""
 
 class Owner(@test.anno.EntryPoint val xx: Int) {
     @test.anno.EntryPoint val yy = 42
+}
+
+@test.anno.EntryPoint
+class WithGetter {
+    @get:test.anno.EntryPoint
+    val zz = 13
 }