Fix Azgalor melee Rain of Fire target swapping

[Copilot]

Azgalor melee handling was sticky once a bot swapped to a Doomguard: if Rain of Fire later landed on that Doomguard, the bot could keep tunneling the add instead of returning to Azgalor. This change makes melee target selection symmetric under Rain of Fire and removes the hidden helper scope introduced in the prior PR.

• Behavior update: Rain of Fire target swapping

  • When a melee bot is standing in active Rain of Fire while targeting Azgalor, it switches to a Lesser Doomguard if one exists.
  • When a melee bot is standing in active Rain of Fire while targeting a Lesser Doomguard, it switches back to Azgalor.
  • When no Doomguard exists, the bot falls back to moving away from Azgalor.

• Action flow correction

  • Removed the return true path in the Doomguard branch that could consume the action and leave the bot effectively stuck.
  • The action now only claims success when it actually changes target or issues movement.

• Helper cleanup

  • Moved the Azgalor Rain of Fire active-object helper out of the anonymous namespace and declared it in HyjalSummitHelpers for explicit shared use.

Unit* doomguard = AI_VALUE2(Unit*, "find target", "lesser doomguard");
bool isTargetingDoomguard =
    doomguard && (bot->GetVictim() == doomguard || bot->GetTarget() == doomguard->GetGUID());

if (isTargetingDoomguard)
    return Attack(azgalor);

if (doomguard)
    return Attack(doomguard);

return MoveAway(azgalor, 5.0f);