The embedded metadata section is the off-heap equivalent to an on-heap
Code object's metadata section. It contains no executable data, thus
.rodata is the natural home for it. Another motivation is that some
platforms do not grant read permissions on the .text section.

Embedded blob stats before:

  EmbeddedData:
    Total size: 1322944
    Data size:  25952
    Code size:  1296992

And after:

  EmbeddedData:
    Total size: 1323372
    Data size:  121452
    Code size:  1201920

(Slight size increase due to additional padding.)

Bug: v8:11036,v8:10707
Change-Id: Ib6b54a7e947966c7bd2fcc1e7e44c85e352f0063
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2502334Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70822}