Update type information for em_asm functions (#2480)

We were only updating the imported Function's type name
field and failing to update its params and results. This caused the
binary writer to start using the wrong types after #2466.

This PR fixes the code to update both type representations on the
imported function. This double bookkeeping will be removed entirely in
an upcoming PR.

Author: tlively

src/wasm/wasm-emscripten.cpp

@@ -871,7 +871,9 @@ void AsmConstWalker::queueImport(Name importName, std::string baseSig) {
   auto import = new Function;
   import->name = import->base = importName;
   import->module = ENV;
-  import->type = ensureFunctionType(baseSig, &wasm)->name;
+  auto* funcType = ensureFunctionType(baseSig, &wasm);
+  import->type = funcType->name;
+  FunctionTypeUtils::fillFunction(import, funcType);
   queuedImports.push_back(std::unique_ptr<Function>(import));
 }