These maps contain exactly the same information as the strict maps, so
this frees up a few pointers of native context space, gets rid of some
branches in FastNewClosure, and adds missing poisoned properties tests
for async functions.

BUG=v8:2355, v8:4483
R=adamk@chromium.org, bmeurer@chromium.org, littledan@chromium.org

Review-Url: https://codereview.chromium.org/2608333002
Cr-Commit-Position: refs/heads/master@{#42051}