[Wasm] Add external file checker to K2

#KT-56849

compiler/testData/diagnostics/wasmTests/jsInterop/module/jsModuleNonExternal.kt

@@ -0,0 +1,10 @@
+// FIR_IDENTICAL
+@file:JsModule("lib")
+
+class <!NON_EXTERNAL_DECLARATION_IN_INAPPROPRIATE_FILE!>A<!> {
+    class B
+
+    fun bar() {}
+}
+
+<!NON_EXTERNAL_DECLARATION_IN_INAPPROPRIATE_FILE!>fun foo()<!> = "OK"