Add reward.cost reward.id, reward.title filter variables

[Mm2PL]

This grows the Message struct by 16 bytes for the shared_ptr.

This adds the following filter variables:

• reward.title
• reward.id
• reward.cost

The use cases include having a separate split for high cost rewards that you don't want to miss, showing only some rewards in chat.

(felanbird): #4882 #4883

[Felanbird]

title works
cost works but probably needs to be an int i see what i did wrong
id works

[pajlada]

Haven't tested yet but this seems fine to me 👍

[pajlada]

I have confirmed that all of these filters work as expected 👍 Thank you!