KT-12152 : constructor consistency analysis, base cases

compiler/testData/diagnostics/tests/constructorConsistency/afterInitialization.kt

@@ -0,0 +1,6 @@
+class My(val x: Int) {
+    val y: Int = x + 3
+    val z: Int? = foo()
+
+    fun foo() = if (x >= 0) x else if (y >= 0) y else null
+}