The module's "prefix hash" is based on a prefix of the module bytes that
starts at the beginning of the module and stops at the code section.

In the case of the streaming decoder, if the code section is empty,
`AsyncStreamingProcessor::ProcessCodeSectionHeader()` is never called,
and we keep accumulating bytes in the hash after the code section. Fix
this by always calling into the streaming processor even if the code
section is empty.

R=ahaas@chromium.org
CC=clemensb@chromium.org

Bug: chromium:1334651
Change-Id: Id2a03468b355867868e589523c994c268c7b4eaf
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3695564
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81060}