With top-level await enabled by default, the behavior of
v8::Module::Evaluate is changed to always return a Promise, and should
be documented.

No-try: true
Change-Id: I8bf41a18d8d98befecd62d6423ab37fdbaac3aad
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2854874Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Auto-Submit: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74238}