Since SlotSet is just an array of Buckets, RecordWrite doesn't need
to calculate the SlotSet-address in the SlotSet-array. bucket_index is
now directly calculated from the offset of the slot from the start of
the page. bucket_index may therefore now also exceed SlotSet::kBuckets,
for large objects.

Also calculate cell_offset and bit_index from page_start_offset, it is
not necessary to truncate page_start_offset to MemoryChunk::kPageSize.

Bug: v8:9454
Change-Id: I17edeafa4681a6348482c64dd0616065ce3121c5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1849525
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64197}