The BytecodePipeline is no longer used by any optimizers, so remove it and
connect the BytecodeArrayBuilder directly to the BytecodeWriter.

Also remove some functions from BytecodeNode which are no longer used.

BUG=v8:6194

Change-Id: Id2ec94ff1d4db41b108a778100459283fbb2256c
Reviewed-on: https://chromium-review.googlesource.com/471528Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44619}