[Wasm] Support callable references to external functions

1. Move jsInteropFunctionsLowering after callable reference lowering,
  so it can continue to deal with just functions and function calls.
2. Generate lowered closure class in JsInteropFunctionsLowering because

compiler/testData/codegen/boxWasmJsInterop/functionTypes.kt

@@ -199,25 +199,42 @@ fun box(): String {
     )
     if (externalWithLambdas2Count != 11) return "Fail externalWithLambdas2"
 
-
-    val jsLambda = createJsLambda()
-
-    val jsLambdaCount = jsLambda(
-        true,
-        100.toByte(),
-        200.toShort(),
-        'я',
-        300,
-        400L,
-        500.5f,
-        600.5,
-        "700",
-        create123Array(),
-        DC(800, 800),
+    val externalWithLambdas2Ref = ::externalWithLambdas2
+    val externalWithLambdas2RefCount = externalWithLambdas2Ref.invoke(
+        { true },
+        { 100.toByte() },
+        { 200.toShort() },
+        { 'я' },
+        { 300 },
+        { 400L },
+        { 500.5f },
+        { 600.5 },
+        { "700" },
+        { create123Array() },
+        { DC(800, 800) },
         { it.y }
     )
-    if (jsLambdaCount != 11)
-        return "Fail 3"
+    if (externalWithLambdas2RefCount != 11) return "Fail externalWithLambdas2"
+
+    val createJsLambdaRef = ::createJsLambda
+    for (jsLambda in arrayOf(createJsLambda(), createJsLambdaRef.invoke())) {
+        val jsLambdaCount = jsLambda(
+            true,
+            100.toByte(),
+            200.toShort(),
+            'я',
+            300,
+            400L,
+            500.5f,
+            600.5,
+            "700",
+            create123Array(),
+            DC(800, 800),
+            { it.y }
+        )
+        if (jsLambdaCount != 11)
+            return "Fail 3"
+    }
 
     complexHigherOrerTest()