Changes:
- Implement a single function
  WriteGlobalValue(const WasmGlobal&, const WasmValue&). Compute an
  intermediate WasmValue when needed.
- Add WasmValue::CopyTo() to avoid reading little endian values in
  WasmValue, and then transforming back to little endian.
- Add WasmValue::to_string() for tracing.

Change-Id: Ia7d9b9cddc7b8f77ae35fc588fe34c41ef444a2c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2948664
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75047}