This moves the static handle() helper function to handles-inl.h as
it ultimately depends on handles-inl.h anyway. To make this
possible, also move some other code to -inl.h files and split up
some header files into a -inl.h part.

Bug: v8:7490
Change-Id: I0f68e0728ba082b87ffa911aaf205d9b1523d2c9
Reviewed-on: https://chromium-review.googlesource.com/1146723Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Stephan Herhut <herhut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54617}