This CL adds the ArrayBufferExtension class, which is used to track
JSArrayBuffers in a linked list. The ArrayBufferExtension is going to
replace the ArrayBufferTracker in the future but is currently behind
the v8_enable_array_buffer_extension feature flag.

When enabled, each JSArrayBuffer has a corresponding native-heap
allocated ArrayBufferExtension object. All extensions are currently
tracked in a single linked list. During marking the GC not only
marks the JSArrayBuffer but also its extension object. At the end of
mark-compact the GC iterates all extensions and removes unmarked ones.

Change-Id: I88298be255944d5ae1327c91b0d7f0fdbcd486d5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1969791Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65724}