[1.21/1.22] Attachment Holders and Codecs

[robotgryphon]

Been digging around data attachments. Now that data attachments no longer apply to item stacks (since components) and the main concern with item data serialization using codecs was how often item NBT got synced.. can we flatten data attachments to always use codecs?

Some reasoning:

• Items no longer use attachments, they use Mojang's components.
• Removing or adapting IAttachmentSerializer in favor of always using codecs is less maintenance
• Favoring codecs also means not dealing with HolderLookup.Provider in many scenarios -- at least, you'd only deal with that while saving NBT, and that's on AttachmentHolder and things using it
• Enabling AttachmentHolder.CODEC support for modder code

Example of a pain point: https://github.com/CompactMods/CompactMachines/blob/83ef9a0daa6162b27d51cd859a39bcdb3fc0621e/neoforge-main/src/main/java/dev/compactmods/machines/data/room/RoomDataAttachments.java#L24-L33

[robotgryphon]

Related PR for code discussion and changes: #1163