Changes output from
CALL RUNTIME (context function) code = 0x3e9ea90a2049 at -1
to
CALL RUNTIME async_function_promise_create code = 0x3e9ea90a2049 at -1

This makes the ast more useful. I didn't annotate all the runtime calls,
only some for now. We can annotate others if necessary.

Review-Url: https://codereview.chromium.org/2654113002
Cr-Commit-Position: refs/heads/master@{#42671}