Migrate ArmorStand meta to using entity tag

[electronicboy]

Our handling of this class causes some headaches due to ItemMeta being lossy, we can double patch this by properly storing the data we care about, there is still some stuff to be addressed, i.e. we really should ensure that the entity tag is stored to the tag properly

TODO: actually, we should just serialise the entity tag directly as b64

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Download the paperclip jar for this pull request: paper-11107.zip