Removes most explicit calls to GetIsolate/GetHeap from heap/ and implicit
calls via the single argument Handle constructor and handle function by
passing it in through calling functions.

(One GetHeap remains in FreeList in heap/spaces.cc for now).

Bug: v8:7786
Change-Id: I14fd099d26f94b9afbcfad41aa873c8f843297dd
Reviewed-on: https://chromium-review.googlesource.com/1087002Reviewed-by: Hannes Payer <hpayer@chromium.org>
Commit-Queue: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53565}