[core, lua] Exdata definitions part 5 [Furniture/Flowerpot/Mannequins]

[sruon]

I affirm:

• I understand that if I do not agree to the following points by completing the checkboxes my PR will be ignored.
• I understand I should leave resolving conversations to the LandSandBoat team so that reviewers won't miss what was said.
• I have read and understood the Contributing Guide and the Code of Conduct.
• I have tested my code and the things my code has changed since the last commit in the PR and will test after any later commits.

What does this pull request do?

Exdata definitions for:

• Furnitures
• Flowerpot
• Mannequins

Misc:

• Fix signatures offset on CItemFurnishing by overriding get/setSignature
• Moved some encoding/decoding logic to CItem and associated (except for linkshells at the moment)
• Created a new packet constructor taking a mannequin directly so we're not passing each fields individually
• Moved the byte we use to track the order in which furnitures were placed (for Moghancement tiebreaking) to a different padding byte as it was conflicting with the Signature range
• Enabled pose in the mannequin packet

Steps to test these changes

• Did the mannequin quest, placed it in MH, equipped gear. Rendered correctly.
• Crafted furnitures with HQ crystals, ensured signatures showed before and after placing them.
• Created a custom flowerpot with a temporary command, verified it was on the right step. Dried the plant, emptied it etc.