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

compiler/testData/diagnostics/tests/dataFlowInfoTraversal/Assignment.fir.kt

@@ -0,0 +1,17 @@
+interface A
+interface B : A {
+    fun foo()
+}
+
+fun bar1(a: A) {
+    var b: B = a as B
+    a.foo()
+    b.foo()
+}
+
+fun id(b: B) = b
+fun bar2(a: A) {
+    var b: B = id(a as B)
+    a.foo()
+    b.foo()
+}