This runtime function now also works for Ignition generators. It returns the
source position of the yield at which a suspended generator got suspended.  This
works by storing the current bytecode offset at suspension and using an existing
mechanism to map it back to a source position.

TBR=littledan@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2079613003
Cr-Commit-Position: refs/heads/master@{#37140}