Make --max_old_space_size and friends work with values >= 2**31.
Such values did not work reliably (or sometimes not all) due to
signed integer overflow in size computations, which is UB.

Fixes https://github.com/nodejs/node/issues/18786.

Bug: chromium:814138
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: Ibe23cef2417fd5b4a727022b8b0d4b50f1417182
Reviewed-on: https://chromium-review.googlesource.com/927063
Commit-Queue: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51433}