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

compiler/testData/diagnostics/tests/declarationChecks/DataFlowInMultiDeclInFor.fir.kt

@@ -0,0 +1,15 @@
+// KT-2667 Support multi-declarations in for-loops in control flow analysis
+package d
+
+class A {
+    operator fun component1() = 1
+    operator fun component2() = 2
+    operator fun component3() = 3
+}
+
+fun foo(list: List<A>) {
+    for (var (c1, c2, c3) in list) {
+        c1 = 1
+        c3 + 1
+    }
+}