This is a reland of ea55438a. Relanding
after a fix lands here:
https://chromium-review.googlesource.com/c/v8/v8/+/3030711. The failures
were caused because baseline code could be flushed during the process
of deoptimization after we choose which entry (InterpreterEnterAt* /
BaselineEnterAt* ) builtin to use. BaselineEnterAt* builtins expect
baseline code but it could be flushed before we execute the builtin. The
fix is to defer the decision.

Original change's description:
> [sparkplug] Support bytecode / baseline code flushing with sparkplug
>
> Currently with sparkplug we don't flush bytecode / baseline code of
> functions that were tiered up to sparkplug. This CL adds the support to
> flush baseline code / bytecode of functions that have baseline code too.
> This CL:
> 1. Updates the BodyDescriptor of JSFunction to treat the Code field of
> JSFunction as a custom weak pointer where the code is treated as weak if
> the bytecode corresponding to this function is old.
> 2. Updates GC to handle the functions that had a weak code object during
> the atomic phase of GC.
> 3. Updates the check for old bytecode to also consider when there is
> baseline code on the function.
>
> This CL doesn't change any heuristics for flushing. The baseline code
> will be flushed at the same time as bytecode.
>
> Change-Id: I6b51e06ebadb917b9f4b0f43f2afebd7f64cd26a
> Bug: v8:11947
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2992715
> Commit-Queue: Mythri Alle <mythria@chromium.org>
> Reviewed-by: Andreas Haas <ahaas@chromium.org>
> Reviewed-by: Toon Verwaest <verwaest@chromium.org>
> Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#75674}

Bug: v8:11947
Change-Id: I63dce4cd9f6271c54049cc09f95d12e2795f15d1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3035774Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Mythri Alle <mythria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75810}