Refactor: make a common TriggeredAbility for "Whenever [X] or more creatures attack,"

Those have all their own trigger implementation:

https://scryfall.com/search?q=o%3A%2Fwhenever%5B%5E%2C%5D*or+more+creatures+attack%2C%2F&unique=cards&as=grid&order=name

We could make a common TriggeredAbility for those, maybe group them with https://scryfall.com/search?q=o%3A%2Fwhenever%5B%5E%2C%5D*or+more%5B%5E%2C%5D*attack%2C%2F&unique=cards&as=grid&order=name ?

Note: preserve the double Outcome on Duelist's Heritage depending on whose turn it is.

Locate the separate implementations matching the linked Scryfall searches and compare their trigger behavior. Inspect Duelist's Heritage in particular before consolidating them, then verify that the shared TriggeredAbility preserves its double Outcome depending on whose turn it is.

Written by the indexing model from the issue text.