Refactor: make a common trigger for 'Whenever you cast your first [FILTER] spell (each turn/during each opponent’s turn),'

https://scryfall.com/search?q=o%3A%22whenever+you+cast+your+first%22

I think most of those could be refactored with a shared trigger using `SpellsCastWatcher` to check that the cast spell is the first matching a filter.

Start by reviewing the Scryfall search results and locating the existing SpellsCastWatcher implementation. Compare the matching card triggers to determine which behavior can share a common trigger, including the per-turn and opponent-turn distinctions. Done means the applicable triggers use the shared implementation and existing behavior remains covered by the relevant tests.

Written by the indexing model from the issue text.