Psi2Ir: Mark accessors with no bodies as default accessors.

They are currently marked as defined even when they get a
default implementation. That makes it hard to figure out
if the accessor should be removed when introducing a backing
field in the JVM_IR backend.

compiler/testData/codegen/box/annotations/annotationsOnLateinitAccessors.kt

@@ -0,0 +1,31 @@
+// WITH_REFLECT
+// IGNORE_BACKEND: JVM_IR
+// TARGET_BACKEND: JVM
+
+// Please make sure that this test is consistent with the diagnostic test "annotationsTargetingLateinitAccessor.kt"
+
+import kotlin.reflect.KAnnotatedElement
+
+annotation class Ann
+
+fun check(element: KAnnotatedElement, annotationExists: Boolean) {
+    require(element.annotations.isNotEmpty() == annotationExists) { "Fail: $element" }
+}
+
+class LateinitProperties {
+    @get:Ann
+    lateinit var x0: String
+
+    @get:Ann
+    private lateinit var x1: String
+
+    fun test() {
+        check(::x0.getter, annotationExists = true)
+        check(::x1.getter, annotationExists = false)
+    }
+}
+
+fun box(): String {
+    LateinitProperties().test()
+    return "OK"
+}