This is a reland of commit a19316d9

- Revert malloc_usable_size() changes temporarily to land them in
  isolation.
- Add cosmetics from https://crrev.com/c/3827876

Original change's description:
> [heap] Rework Worklist base type
>
> Worklist uses a singly-linked list of segments to hold entries.
> Segment size was based on a compile-time constant but already stored
> in the segment itself.
>
> Rework the segments to query `malloc_usable_size()` on allocation and
> adjust the capacity properly. For PartitionAlloc, it turns out that
> there's ~20% more capacity available for the 64-element segments.
>
> This slows down actual allocation of the segments with the upside of
> improving utilization and requiring 20% less segments.
>
> Change-Id: Ib8595c3fb9fb75b02e4022f6c525bb59a2df7ab7
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3826047
> Commit-Queue: Anton Bikineev <bikineev@chromium.org>
> Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
> Reviewed-by: Anton Bikineev <bikineev@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#82432}

Change-Id: Ic8c5257cfe3c347b11eea5c513ca7f62e09f637f
Bug: v8:13193
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3829475Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82493}