Update 2 for TrinityCore WotLK Single Player Repack

• Magister's Terrace: Migrate linked_respawn to spawn groups.
• Halls of Stone: Migrate linked_respawn to spawn groups.
• Drak'Tharon Keep: Migrate linked_respawn to spawn groups.
• Azjol-Nerub: Migrate linked_respawn to spawn groups.
• Halls of Lightning: Migrate linked_respawn to spawn groups.
• Gundrak: Delete redundant linked_respawn data, already handled by spawn groups.
• Ahn'kahet: The Old Kingdom: Migrate linked_respawn to spawn groups.
• Icecrown Citadel: Migrate linked_respawn to spawn groups.
• The Blood Furnace: Added spawn groups for bosses.
• The Arcatraz: Added missing boss spawn group.
• Halls of Reflection: Added spawn groups for bosses.
• Zul'gurub: Added spawn groups for bosses and prevent multiple Gahz'ranka summons.
• Ruins of Ahn'Qiraj: Added spawn groups for bosses.
• Ahn'Qiraj Temple: Added spawn groups for bosses.
• Serpentshrine Cavern: Add spawn group for Lady Vashj.
• Ulduar: Add spawn group for bosses.
• Trial of the Crusader: Add spawn group for Anub'arak.
• Naxxramas: Added spawn groups for Sapphiron and Kel'Thuzad.

SCRIPTS

• Halls of Stone: Modernized Halls of Stone instance script.
• Halls of Lightning: reworked Volkhan encounter
• Modernized the whole code.
• Moved several mechanics to spell script where they belong.
• Handle missing visuals for Volkhan's Anvil.
• The Underbog: Added spawn groups for bosses and implemented boss state tracking.
• The Escape From Durnholde: Minor improvements.
• Converted to BossAI.
• Prevent repeating boss kills on Thrall event wipe.
• Halls of Reflection: Prevent repeating Falric kills after wiping on Marwyn or add waves > 5.
• Karazhan: Mark optional boss as completed when it dies.
• Hyjal: Change boss state management from SetData to SetBossState.

CORE

• Guilds: Improve HandleRoster performance.
• Players: Added error message for death knights attempting to leave their starting zone early.