Removes all explicit calls to GetIsolate() in builtins/ by passing it
through from calling functions and implicit calls via the Handle
constructor.

Bug: v8:7786
Cq-Include-Trybots: luci.v8.try:v8_linux_noi18n_rel_ng
Change-Id: I32e1cdee47075742e677a5f738a33ad30be515c6
Reviewed-on: https://chromium-review.googlesource.com/1079548Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53456}