Don't return NoChange when the new_target input to a JSConstruct node is
already a HeapConstant, but rather use that constant in the interesting
lowering below. This was introduced accidentally by 

  https://chromium-review.googlesource.com/604790

earlier. Also don't use ShouldUseCallICFeedback predicate here, as that
doesn't really make sense for JSConstruct, but is mostly interesting for
JSCall (hence the name).

Bug: v8:5517, v8:6399, v8:6679
Change-Id: I96201281cf1a10f2bfd2dc3859455161eb310ccf
Reviewed-on: https://chromium-review.googlesource.com/607887Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47237}