Further optimize the

  new Array(n)

expressions by also inlining the backing store allocation into TurboFan
optimized code. Currently these backing store allocations cannot be
eliminated by escape analysis and can also not be optimized further by
the memory optimizer (i.e. no allocation folding and not write barrier
elimination) yet, but this can be done in follow-up CLs.

This yields another ~5% improvement on the ARES6 ML benchmark (steady
state).

Drive-by-fix: Add support for loops to the GraphAssembler. This was
necessary to implement the initialization loops in for the backing
store allocations in the EffectControlLinearizer.

Bug: v8:6399, v8:6901
Change-Id: I759d6802db01eb797e78c7d82d82caaee3463e16
Reviewed-on: https://chromium-review.googlesource.com/705934Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48352}