Function add_splice_effect 

pub fn add_splice_effect(
    sa: &mut SpellAbility,
    game: &GameState,
    splice_card_id: CardId,
)

Add a single splice effect from a card onto a spell ability. Mirrors Java’s AbilityUtils.addSpliceEffect(SpellAbility, Card).

Appends the first spell ability of the spliced card as a sub-ability at the end of the SA chain, and adds the splice cost to the total cost.