JVM_IR: bug fix in classFileContainsMethod

The old test sequence failed for toplevel functions because of file
class wrappers, so that the second branch was never invoked.

compiler/testData/codegen/box/inlineClasses/multifileClass.kt

@@ -0,0 +1,10 @@
+// WITH_RUNTIME
+// IGNORE_BACKEND: JVM
+
+fun box(): String {
+    val uia = uintArrayOf()
+    val uia2 = uintArrayOf()
+    // UIntArray is a multifile class, so we need to know where to search for extension method copyInto.
+    uia.copyInto(uia2)
+    return "OK"
+}