Generate constructors with empty bodies for annotation classes

Default parameter values of primary constructor of an annotation class
are required to generate default values of annotation properties.

compiler/testData/ir/irText/classes/annotationClasses.kt

@@ -0,0 +1,7 @@
+annotation class Test1(val x: Int)
+
+annotation class Test2(val x: Int = 0)
+
+annotation class Test3(val x: Test1)
+
+annotation class Test4(vararg val xs: Int)