[wasm] Refactor import handling for 0xC.

test/mjsunit/wasm/instance-gc.js

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Flags: --expose-wasm --expose-gc
 
 load("test/mjsunit/wasm/wasm-constants.js");
 load("test/mjsunit/wasm/wasm-module-builder.js");
 
 let nogc = () => {};
 
 function newModule() {
   let builder = new WasmModuleBuilder();
   builder.addMemory(1, 1, true);
-  builder.addFunction("main", kSig_i)
+  builder.addFunction("main", kSig_i_v)
     .addBody([kExprI32Const, 0, kExprI32LoadMem, 0, 0])
     .exportFunc();
 
   return new WebAssembly.Module(builder.toBuffer());
 }
 
 function newInstance(module, val) {
   var instance = new WebAssembly.Instance(module);
   var view = new Int32Array(instance.exports.memory.buffer);
   view[0] = val;
@@ skipping 87 matching lines @@
     roots[1] = newInstance(module, 22222);
     assertEquals(11111, roots[0].exports.main());
     assertEquals(22222, roots[1].exports.main());
     roots[0] = null;
     roots[1] = null;
   })();
 }
 
 TestReclaimingCompiledModule(nogc);
 TestReclaimingCompiledModule(gc);