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

compiler/testData/diagnostics/tests/secondaryConstructors/unreachableCode.fir.kt

@@ -0,0 +1,38 @@
+class A0 {
+    val x: Int
+    constructor() {
+        if (1 == 1) {
+            return
+        }
+        x = 1
+    }
+    constructor(arg: Int) {
+        x = arg
+    }
+}
+
+class A1 {
+    val x: Int
+    constructor() {
+        if (1 == 1) {
+            return
+        } else null!!
+        x = 1
+    }
+}
+
+class A2 {
+    val x: Int
+    constructor() {
+        if (1 == 1) {
+            x = 1
+            return
+        }
+        else {
+            x = 2
+        }
+    }
+    constructor(arg: Int) {
+        x = arg
+    }
+}