The streaming decoder did not properly check the ordering of sections
relative to the code section.
This CL fixes that for both empty and non-empty code sections.
The special path for empty code sections is not actually needed, so
remove it to simplify code paths.

Drive-by:
1. Refactor the existing code for checking section ordering to make it
   more structured and readable.
2. Ensure that we either call {DecodeCodeSection} or {StartCodeSection},
   but not both.
3. Remove {set_code_section}, merge it into {StartCodeSection}.
4. Simplify calls to {CalculateGlobalOffsets} (make them unconditional
   and remove one redundant one).

R=ahaas@chromium.org

Bug: chromium:1336380
Change-Id: Ia2c5c115d43d2b5315e3b3c9e4a21175a36aa326
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3747860Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81554}