This adds optimizations that apply the reductions
  (x + Int32Constant(a)) + Int32Constant(b)) => x + Int32Constant(a + b)
  (x + Int64Constant(a)) + Int64Constant(b)) => x + Int64Constant(a + b)
to the TurboFan graph.

This helps reducing awkward sequences like
  leaq r12,[r9*8+0x8]
  movq r12,[rbx+r12*1-0x1]
to
  movq r12,[rax+r9*8+0x7]


Change-Id: Iaa3a1cb9136a3f905ba33c62e16c3cb3c117605c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1627544
Auto-Submit: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61817}