[Feature request] Dealing with the backlog after rescheduling

[Expertium]

I think that most users see a huge backlog after rescheduling their cards when switching from Anki to FSRS or from FSRS v3 to FSRS v4. I think we need an additional load balancing feature when rescheduling a large (say, >1000 cards) amount of cards to spread the reviews across several days or a week so that switching from one algorithm to a different one is less "painful" in the sense that the user doesn't have to immediately do a lot of reviews. Also, someone on Reddit mentioned a problem with rescheduling and a large backlog, but it seems that they didn't make a github issue.

Originally posted by @Expertium in https://github.com/open-spaced-repetition/fsrs4anki/issues/282#issuecomment-1666849832