fix: Fix RPGdie iuse

[KheirFerrum]

Checklist

Required

• I wrote the PR title in conventional commit format.
• I ran the code formatter.
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Purpose of change

• Fix Dice are consumed on activation #5789 which was a bug exposed by fix: Make rags consume their charges/delete themselves. #5589. iuse actions in iuse.cpp return an int value that indicates charges to be used from an item, but this wasn't properly being used due to a lack of consideration in use_charges().
• The RPG die iuse returns the roll value for no reason whatsoever, as nothing the iuse does is contingent on that return. It's likely some legacy thing from when each iuse had it's own special return function.

Describe the solution

• iuse::rpgdie now returns 0 in all cases, preventing charges of rpgdie from being used.

Describe alternatives you've considered

• Reverting fix: Make rags consume their charges/delete themselves. #5589
  • Would be a dumb idea given that the behaviour it fixes is not expected behaviour.
• Rework iuse::rpgdie
  • It's on my list, as of current, the die faces and values are totally random, I'll likely convert it into an iuse_actor later on so that you can define individual dice with fixed sides instead of each die being set randomly to being a d4, d8, d20, d50 etc.

Testing

• Spawn and roll die and confirm they aren't being used up.

Additional context

I shudder to think what other bugs have been uncovered in the process. Most should be fixed with the energy rework, but that's going to break 50 other things I didn't account for I'm sure.

[scarf005]

LGTM