Core: Remove CCharEntity::pushPacket(raw packet)

[zach2good]

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?

Closes #6545

After looking here: I realised how easy it still is to leak packets: #6711

A big step towards: #5171

The scope of this blew up, as always. Now, CBasicPacket is ONLY a wrapper around std::array<uint8, PACKET_SIZE> buffer_;. It doesn't do non-owning, I've audited how they're constructed, etc. We also now NEVER new a packet - it's always constructed as a unique_ptr, and we are careful to pass around references or move them as needed. This also means that we have to be obvious when we wither std::move() or ->copy() packets in places.

But now, there's no question about what happens where - we can see what our data is doing.

Testing

• Log in
• /wave
• Zone into {Dynamis - Bastok}
• Spells -> targeting failure
• RA -> targeting failure
• Action packet
• Mounts
• Chocobo raising menu
• Train everything around
• Crafting
• Interacting with NPCs
• Moghouse
• Party
• Trusts
• Linkshell
• IPC/ZMQ
• Tell/Party/Shout/Yell
• Events with updates (BCNM entry, Instance entry)
• BCNMs
• Instances
• Trading
• AH
• Monstrosity

[zach2good]

This is now very well tested and ready for review