Paper.ignoreWorldDataVersion should also disable the item data version checks in CraftMagicNumbers

[MrPowerGamerBR]

Is your feature request related to a problem?

If you need to downgrade your server for some reason (I know, I know... this is unsupported) you can enable the Paper.ignoreWorldDataVersion system property to let Paper ignore the world data version, allowing an older Paper version to load a world with a newer data version than the server.

However, CraftMagicNumbers still checks the item data version to see if it is newer than the data version of the server, causing issues when downgrading the server. This causes errors when you attempt to deserializeBytes an item stack that was serializeAsBytes'd on a recent version.

Describe the solution you'd like.

To be consistent, the data version checks in CraftMagicNumbers should also respect the Paper.ignoreWorldDataVersion property, or maybe a new property should be added (Paper.ignoreItemDataVersion?).

Describe alternatives you've considered.

Not downgrading the server. (yeah that also works but that ain't fun)

Other

This is mostly something that would be useful for users that really need to downgrade the server and that for some reason can't restore from a backup, I encountered that version check issue when I attempted to downgrade from 1.21 to 1.20.6.

Example patch that disables the item version check: https://github.com/SparklyPower/SparklyPaper/blob/1b3fb6b9aac96ba8aa175fc6cf316dd6d43c138a/patches/server/0025-Allow-item-version-downgrades.patch