This adds a new Code section to the compilation cache (aka isolate
cache), and inserts generated native context independent code into it.

Cache consumption will be implemented in a following CL.

Bug: v8:8888
Change-Id: I997c13da0fe547f395627a48f1cb7e5f19dfc3ba
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2288851Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68824}