fix(Core/Spell): Allow using SpellDifficulty in bg (#19422)

* fix(Core/Spell): Allow using SpellDifficulty in bg

* cherry-pick commit (https://github.com/TrinityCore/TrinityCore/commit/e4caf52e5a3820399d7ddd5ea3963c36d1d71e28)

* "Allow get SpellDifficulty on battleground maps
This is only for Isle of Conquest (Bracket 71-79 is Regular Difficulty, Bracket 80-84 is heroic or 25Man)
Spells of IoC Battleground vehicles, cannons, bombs and bosses have SpellDifficulty in DBC"

* Remove redundant CastSpell and assign a variable instead

Co-Authored-By: Gildor <521036+Jildor@users.noreply.github.com>

* Update isle_of_conquest.cpp

---------

Co-authored-by: Gildor <521036+Jildor@users.noreply.github.com>

data/sql/updates/pending_db_world/rev_1721214859612463300.sql

@@ -0,0 +1,5 @@
+--
+DELETE FROM `spell_script_names` WHERE `ScriptName`='spell_ioc_bomb_blast_criteria' AND `spell_id` IN (67813,67814);
+INSERT INTO `spell_script_names` (`spell_id`, `ScriptName`) VALUES
+(67813, 'spell_ioc_bomb_blast_criteria'),
+(67814, 'spell_ioc_bomb_blast_criteria');