Track generator ID using RecordReplayObjectId

[bhackett1024]

We need to associate IDs with each generator object in order to support async stepping. Currently we do this by storing an integer in JSGeneratorObject which is accessed when starting/resuming generators, but the modification this makes to js-generator.tq seems to be causing frequent scavenger crashes. We have a separate, slower weak map from objects to IDs which we can use instead and avoid modifying this tq file.