Make lateinit diagnostics more clear

compiler/testData/codegen/box/properties/lateinit/simple.kt

@@ -1,12 +0,0 @@
-class A {
-    public lateinit val str: String
-
-    init {
-        str = "OK"
-    }
-}
-
-fun box(): String {
-    val a = A()
-    return a.str
-}

compiler/testData/codegen/box/properties/lateinit/simpleField.kt

@@ -1,16 +0,0 @@
-class A {
-    private lateinit val str: String
-
-    init {
-        str = "OK"
-    }
-
-    public fun getMyStr(): String {
-        return str
-    }
-}
-
-fun box(): String {
-    val a = A()
-    return a.getMyStr()
-}