Flag modded levels + per-user mod filtering
Adds a flag to all levels to state whether they contain modded content of any kind. Also adds a user setting + command to hide all modded content from the game, if the user does not wish to see any modded content in level results.
This PR also fixes MATT asset uploads and optimizes our realm migrations.
Marking as draft until I split the realm changes out to another PR
Misflagging of vanilla assets has been solved. This PR also relaxes the mod filter slightly, as it has been discovered that a couple extra asset types can (very rarely) be uploaded by the game on an unmodified copy. After those changes, only ~10% of all levels on prod are marked as "modded", compared with the ~12% before those changes.