Fix trashcan delete reaction in DMs

[mhaxanali]

Relevant Issues

Closes #1450

Description

Added on_raw_reaction_add handler to support reaction events in DMs, as the standard on_reaction_add doesn't fire in DM contexts.

Original Implementation @ OSCxSST/sir-lancebot-SLB/pull/20

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[Akarys42]

As it stands currently, considering you have both on_raw_reaction_add and on_reaction_add, wouldn't the action be performed twice if the message is inside a guild?

[mhaxanali]

As it stands currently, considering you have both on_raw_reaction_add and on_reaction_add, wouldn't the action be performed twice if the message is inside a guild?

Yes, I just tested that, and I think on_reaction_add should be removed then. Also the try-except block removed previously for deleted reactions needs to be added again for this change, which I have done. Few imports also became unused after this change so removing them as well.