[api] Adding total allocated bytes in HeapStatistics

This change exposes total allocated bytes in v8::HeapStatistics API by
introducing a new total_allocated_bytes() method that tracks all heap
allocations since an Isolate creation.

The implementation adds:
- uint64_t total_allocated_bytes_ field to HeapStatistics.
- An atomic total allocation counter is stored in the Heap class.
- The counter is incremented whenever a RestLab is called. This approach can overestimate the total allocation for cases where the LAB is not fully used, but the leftover compared to the LAB itself is quite small, so it seems tolerable.

Design doc reference:
https://docs.google.com/document/d/1O4JPsoaxTQsX_7T5Fz4rsGeHMiM16jUrvDuq9FrtbNM

Change-Id: Ic531698aaeb1578f943b7fdd346b9159ffd9b6c9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/6996467
Reviewed-by: Dominik Inführ <[email protected]>
Reviewed-by: Michael Lippautz <[email protected]>
Commit-Queue: Dmitry Bezhetskov <[email protected]>
Cr-Commit-Position: refs/heads/main@{#103296}