Add support for fast

  - get Map.prototype.size
  - get Set.prototype.size

by porting both the baseline implementation to the CodeStubAssembler and
inlining a fast-path into TurboFan (when the compiler can infer the fact
that the receiver is a proper JSCollection from the surrounding graph,
i.e. from feedback gathered by a dominating LOAD_IC).

R=yangguo@chromium.org

Bug: v8:5269, v8:5717
Change-Id: Ie003fd2551462591273bcb8487b80808dcc6cd82
Reviewed-on: https://chromium-review.googlesource.com/566438
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46555}