Atomics.wait is a function which may block, which is not allowed on the
main thread. Since V8 doesn't know whether a particular isolate is the
"main thread", this CL adds an option to Isolate::CreateParams to choose
whether this function is allowed.

Review-Url: https://codereview.chromium.org/2642293002
Cr-Commit-Position: refs/heads/master@{#42611}