This is a reland of c07c02e1

Original change's description:
> [runtime] Remove extension slots from context objects
>
> Context objects have an extension slot, which contains further
> additional data that depends on the type of the context.
>
> This CL removes the extension slot from contexts that don't need
> them, hence reducing memory.
>
> The following contexts will still have an extension slot: native,
> module, await, block and with contexts. See objects/contexts.h for
> what the slot is used for.
> The following contexts will not have an extension slot anymore (they
> were not used before): script, catch and builtin contexts.
> Eval and function contexts only have the extension slot if they
> contain a sloppy eval.
>
> Bug: v8:9744
> Change-Id: I8ca56c22fa02437bbac392ea72174ebfca80e030
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1863191
> Commit-Queue: Victor Gomes <victorgomes@google.com>
> Reviewed-by: Toon Verwaest <verwaest@chromium.org>
> Reviewed-by: Jakob Gruber <jgruber@chromium.org>
> Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> Reviewed-by: Leszek Swirski <leszeks@chromium.org>
> Reviewed-by: Peter Marshall <petermarshall@chromium.org>
> Auto-Submit: Victor Gomes <victorgomes@google.com>
> Cr-Commit-Position: refs/heads/master@{#64372}

TBR=verwaest@chromium.org,jgruber@chromium.org,ulan@chromium.org,leszeks@chromium.org,petermarshall@chromium.org

Bug: v8:9744
Change-Id: I0749cc2d8f59940c25841736634a70047116d647
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1869192Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Auto-Submit: Victor Gomes <victorgomes@google.com>
Cr-Commit-Position: refs/heads/master@{#64380}