AbilityManaPart: use Multiset for produced

[Hanmac]

Part of #10750

This should help with producing big amount of Mana per ManaAbility,
it only creates one Mana Record instance per color type.

the multiset is still expanded when adding them to the ManaPool (for now)

I wanted to do the ManaPool too, but it got too complicated, so i do something smaller

[tool4ever]

as far as I can tell nothing seems to care about duplicate objects there

[Hanmac]

Technically, the Mana records are still duplicated,
just from [M, M] to {M=>2}