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/diagnostics/testsWithStdLib/annotations/annotationsTargetingLateinitAccessors.kt

@@ -0,0 +1,14 @@
+// Please make sure that this test is consistent with the blackbox test "annotationsOnLateinitAccessors.kt"
+
+import kotlin.reflect.KProperty
+
+annotation class Ann
+annotation class AnnRepeat
+
+class LateinitProperties {
+    @get:Ann
+    lateinit var y0: String
+
+    <!ANNOTATION_TARGETS_NON_EXISTENT_ACCESSOR!>@get:Ann<!>
+    private lateinit var y1: String
+}