Adds some necessary padding to ensure the frame is 16-byte aligned.
We don't yet consider the bailout state, which will be handled separately.

This patch also improves the code generated for ContinueTo*Builtin* stubs.

Finally, it adds a test that checks the return value for Array.map in
the case where a LAZY deopt results in a topmost builtin continuation
frame - this is easy to break if the padding for the result is done
incorrectly in NotifyBuiltinContinuation, but was not detected by existing
tests.

Bug: v8:6644
Change-Id: Id1a294950cdf535e2bfdb0ed27c67f077ec34f8a
Reviewed-on: https://chromium-review.googlesource.com/704835
Commit-Queue: Georgia Kouveli <georgia.kouveli@arm.com>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48465}