This adjusts v8::[Shared]ArrayBuffer::NewBackingStore to allow passing
a known empty deleter -- v8::BackingStore::EmptyDeleter. Such API is
useful if the backing store memory is static or is manually managed.

We can skip adjusting the amount of external memory for ArrayBuffers
with empty deleters and thus avoid scheduling ineffective GCs.

Bug: chromium:1061960

Change-Id: I0ef5b2b0839098beb59d5cebbb28f9f81a73a042
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2105355Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66740}