watchPromise during buildRootObject causes start failure

[mhofman]

Describe the bug

Calling watchPromise during buildRootObject causes start vat to fail if the promise is not observed as settled by the time buildRootObject completes. loadWatchedPromiseTable attempts to revive / register all promises in the table, even if the table entry was just created.

This kind of scenario would happen when an orchestrated or async flow replays on restart, or more specifically, when we attempt the shortening of any vow on start.

Upgrade considerations

Any vat that may be doing a watchPromise during start won't be upgradable until liveslots is upgraded with a fix, which requires a chain software upgrade.