Code pages need to be swept on the main thread for now. Originally this
was done to prevent RWX on code pages, but there might be more other
smaller issues like the linked bug. Most likely this restriction isn't
a problem for concurrent SP at the moment, so stick with this
invariant for now.

Bug: chromium:1269558, v8:12054
Change-Id: Icf7a7ce9714b9ef07b1a5070f0b0dd963b6d3011
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3279682
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77901}