[FIR-TEST] Add new testdata generated after changes in previous commit

compiler/testData/diagnostics/tests/controlFlowAnalysis/propertiesInitWithOtherInstance.fir.kt

@@ -0,0 +1,12 @@
+class A(val next: A? = null) {
+    val x: String
+    init {
+        next?.x = "a"
+        x = "b"
+        this.x = "c"
+        x = "d" // don't repeat the same diagnostic again with this receiver
+        this.x = "e"
+
+        next?.x = "f"
+    }
+}