SD-242 Correctly emit InterfaceMethodRef in bytecode after closure inlining

```
⚡ qscalac -opt:l:classpath -d /tmp sandbox/test.scala && javap -v -cp /tmp Test | cat -b | grep -i --color  '$anonfun$test$1'
    26	  #17 = Utf8               $anonfun$test$1
    27	  #18 = NameAndType        #17:#13        // $anonfun$test$1:()V
    28	  #19 = InterfaceMethodref #2.#18         // Test.$anonfun$test$1:()V
    59	  #50 = MethodHandle       #6:#19         // invokestatic Test.$anonfun$test$1:()V
    96	         0: invokestatic  #19                 // InterfaceMethod $anonfun$test$1:()V
   140	  public static void $anonfun$test$1();
   169	      #50 invokestatic Test.$anonfun$test$1:()V
```

Author: retronym

src/compiler/scala/tools/nsc/backend/jvm/opt/ClosureOptimizer.scala

@@ -325,7 +325,7 @@ class ClosureOptimizer[BT <: BTypes](val btypes: BT) {
         insns.insertBefore(invocation, new InsnNode(DUP))
         INVOKESPECIAL
     }
-    val isInterface = bodyOpcode == INVOKEINTERFACE
+    val isInterface = classBTypeFromInternalName(lambdaBodyHandle.getOwner).isInterface.getOrElse(bodyOpcode == INVOKEINTERFACE) // TODO
     val bodyInvocation = new MethodInsnNode(bodyOpcode, lambdaBodyHandle.getOwner, lambdaBodyHandle.getName, lambdaBodyHandle.getDesc, isInterface)
     ownerMethod.instructions.insertBefore(invocation, bodyInvocation)