Bulk change items on actors for null stats migration

Intent

Instead of updating one item at a time, bulk update the items on an actor. This speeds up the migration time considerably.

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• This is meant for a hotfix
• This is meant for the next release (see milestone)
• This needs more reviewers than normal; there may be controversy or high complexity
• This intentionally introduces regressions that will be addressed later
• There is/will be documentation changes on the wiki
• Please do not send commits here without coordinating closely with the owner
• This is a Build System change

Steps to Test

1. Open a world to migrate from v10 to v11

Future Work

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Additional Notes

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