https://github.com/tc39/ecma262/pull/988 gained concensus during the
september 2017 TC39 meetings. This moves the load of the "next" method
to the very beginning of the iteration protocol, rather than during
each iteration step.

This impacts:

- yield*
- for-of loops
- spread arguments
- array spreads

In the v8 implementation, this also affects async iteration versions of
these things (the sole exception being the Async-From-Sync iterator,
which requires a few more changes to work with this, likely done in a
followup patch).

This change introduces a new AST node, ResolvedProperty, which can be used
as a callee by Call nodes to produce the same bytecode as Property calls,
without observably re-loading the property. This is used in several
AST-desugarings involving the iteration protocol.

BUG=v8:6861, v8:5699
R=rmcilroy@chromium.org, neis@chromium.org, adamk@chromium.org

Cq-Include-Trybots: luci.v8.try:v8_linux_noi18n_rel_ng
Change-Id: Ib81106a0182687fc5efea0bc32302ad06376773b
Reviewed-on: https://chromium-review.googlesource.com/687997
Commit-Queue: Caitlin Potter <caitp@igalia.com>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50452}