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.

首先定位 wasm 传输层，并跟踪数据如何在 JavaScript 和 C++ 之间进行编组。先测量临时缓冲区分配和数据复制；在不改变传输行为的情况下减少不必要的分配或复制，即表示完成。