source split change may use stale cache

[xxchan]

          > For existing splits, we should use the latest offset from the cache. `target_splits` is from meta and contains the initial offset.

I'm unsure whether this is always correct when scaling. The ideas are similar to the documentation on the function cache_may_stale. The safest way should be always recovering states from the state store.

Originally posted by @BugenZhao in #14172 (comment)

[github-actions]

This issue has been open for 60 days with no activity. Could you please update the status? Feel free to continue discussion or close as not planned.