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

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

@@ -0,0 +1,18 @@
+// !CHECK_TYPE
+
+interface A
+
+interface B : A
+operator fun B.plus(b: B) = if (this == b) b else this
+
+fun foo(a: A): B {
+    val result = (a as B) + a
+    checkSubtype<B>(a)
+    return result
+}
+
+fun bar(a: A, b: B): B {
+    val result = b + (a as B)
+    checkSubtype<B>(a)
+    return result
+}