Avoid unnecessary memory allocation and copying in wasm transport layer

There are opportunities to improve the performance of the wasm transport layer. It necessarily includes marshalling of data between JavaScript and C++, but I think some of this can be improved as there are some unnecessary allocations of temporary buffers where we can probably just reuse the same buffer, and we may well be doing more copies of data than are strictly necessary.

先定位 wasm 傳輸層，並追蹤資料如何在 JavaScript 和 C++ 之間進行編組。先測量暫存緩衝區配置和資料複製；在不變更傳輸行為的情況下減少不必要的配置或複製，即表示完成。