Replace all but one Handle<T*>(T*) calls with ones that explicitly pass
in an Isolate.

Requires plumbing Isolate* through several Parser functions which
previously avoided it because of worries about accessing the heap off
the main thread. In all off-main-thread cases, isolate will be nullptr
and every such function asserts with:
DCHECK_EQ(parsing_on_main_thread_, isolate != nullptr);

Also deletes unused function ParseInfo::ReopenHandlesInNewHandleScope.

Bug: v8:7786
Change-Id: I3dd9c49dcde49fdbcb684ba73f47a30d00fc495e
Reviewed-on: https://chromium-review.googlesource.com/1087272
Commit-Queue: Dan Elphick <delphick@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53820}