[CardDB] Drop the rebalanced-cards setting entirely (#7457)

* [CardDB] Drop rebalanced-card filtering from the v4 parser

Rebalanced cards no longer exist, so the includeRebalancedCards
preference has no data to filter. Always keep printings marked
isRebalanced and remove the now-unused ICardPreferenceProvider
plumbing from CockatriceXml4Parser and CardDatabaseLoader.

The setting itself (CardsDisplaySettings, Manage Sets checkbox,
Oracle attribute mapping) is removed in a follow-up.

* [CardDB] Drop the rebalanced-cards setting entirely

Rebalanced Alchemy cards no longer exist, so remove the
includeRebalancedCards preference surface: the CardsDisplaySettings
getter/setter/signal, the ICardPreferenceProvider and
ICardsDisplaySettingsProvider methods, the Manage Sets checkbox, the
legacy settings migration mapping, the isRebalanced attribute mapping
in the Oracle importer, and the isRebalanced attribute in the v4
schema.

Builds on #7448, which already stopped the v4 parser from filtering
on the preference.

* [CardDB] Drop the unused isOnlineOnly printing property

The Arena-card detection switched from isOnlineOnly to isRebalanced in
#5778, so nothing has read this printing property since; it only
round-trips from the Oracle importer into cards.xml. Remove the
importer mapping, the benchmark fixture field and the v4 schema
attribute so regenerated databases stop carrying it.

---------

Co-authored-by: Lukas Brübach <Bruebach.Lukas@bdosecurity.de>

cockatrice/src/database/interface/settings_card_preference_provider.h

@@ -13,11 +13,6 @@ public:
     {
         return SettingsCache::instance().cardOverrides().getCardPreferenceOverride(cardName);
     }
-
-    [[nodiscard]] bool getIncludeRebalancedCards() const override
-    {
-        return SettingsCache::instance().cardsDisplay().getIncludeRebalancedCards();
-    }
 };
 
 #endif // COCKATRICE_SETTINGS_CARD_PREFERENCE_PROVIDER_H