CastHistory

- Collapse multi-strike abilities to a single icon per button press. Melee abilities that hit with both weapons or strike several times — Fury warrior's Rampage, Odyn's Fury, Whirlwind, Raging Blow, and Execute, plus off-GCD ones like Charge and Heroic Leap — each fire several `UNIT_SPELLCAST_SUCCEEDED` events, so one press was showing up as several icons. CastHistory now folds the extra strikes into the cast you actually pressed, while still showing genuine re-presses separately.