Presences don't update user cache

Created by: VelvetThePanda

Summary

Presences are a bit borked in the lib. Leave it to me of all people to find out why. :b

Presence updates for better or worse do not update underlying user objects.

The issue lies on this section of code: https://github.com/DSharpPlus/DSharpPlus/blob/2c74a38c0c39ee7812299a72c6f08cbf74296b20/DSharpPlus/Clients/DiscordClient.Dispatch.cs#L1653-L1684

Steps to reproduce

• Pick a user that hasn't sent a message (Updates cache)
• Attempt to pull their presence
• Observe null presence, even if they're online

Alternatively:

• Hook PresenceUpdated
• Observe PresenceBefore and PresenceAfter are not null
• Observe UserBefore.Presence is null
• Observe User.PresenceAfter is not null

Notes

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