This is a reland of c7c47c68.

This makes TSAN happy in addition to:

Previously I presumed that the context read from a frame in the profiler was
a valid context. Turns out that on non-intel we're not guaranteed that the
frame is properly set up. In the case we looked at, the profiler took a
sample right before writing the frame marker indicating a builtin frame,
causing the "context" pointer from that frame to be a bytecode array. Since
we'll read random garbage on the stack as a possible context pointer, I made
the code reading the native context from it a little more defensive.

Bug: v8:9860
Tbr: ulan@chromium.org, neis@chromium.org, ishell@chromium.org

Original change's description:
> [runtime] Move Context::native_context to the map
>
> Remove the native context slot from contexts by making context maps
> native-context-specific. Now we require 2 loads to go from a context to the
> native context, but we have 1 field fewer to store when creating contexts.
>
> Change-Id: I3c0d7c50c94060c4129db684f46a567de6f30e8d
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1859629
> Commit-Queue: Toon Verwaest <verwaest@chromium.org>
> Reviewed-by: Igor Sheludko <ishell@chromium.org>
> Reviewed-by: Peter Marshall <petermarshall@chromium.org>
> Reviewed-by: Maya Lekova <mslekova@chromium.org>
> Reviewed-by: Georg Neis <neis@chromium.org>
> Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> Reviewed-by: Toon Verwaest <verwaest@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#64296}

Change-Id: I4d0ab4cbbb23a9ae616407f17ef8f35a0b68ddb4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1864654
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64360}