Removes handles from bytecode generation, instead storing
un-internalized AstValues (and other, similar values such as Scopes and
AstRawStrings) in the constant array builder.

This will allow us in the future to generate the bytecode before
internalizing the AST.

BUG=v8:5832

Change-Id: I3b8be8f7329a484eb1e5d12808b001d3475239da
Reviewed-on: https://chromium-review.googlesource.com/439326
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43115}