Entity NBT controls and SNBT support

[tal5]

SNBT part requested on Discord.

Additions

• NMSHandler#parseSNBT - parses an SNBT string into a CompoundTag.
• EntityHelper#getRawNBT - gets an entity's raw NBT data.
• EntityHelper#modifyRawNBT - modifies an entity's raw NBT data based on the input CompoundTag.
• EntityTag.all_raw_nbt tag - gets an entity's entire raw NBT data as a MapTag.
• EntityTag.raw_nbt mechanism - modifies an entity's raw NBT data.
• ElementTag.snbt_to_map tag - parses a raw SNBT string into an NBT MapTag.
• EntityHelperImpl(1.20)#getRawEntityNBT - util method to get an entity's entire CompoundTag, used by both new EntityHelper methods.

Changes

• Made the Raw NBT Encoding language meta a bit more generic, as it's no longer just for items.