Revert Visibility Notifier changes (#17682)

* Revert "fix(Core/Grid): Implement missing GridUnload setting (#17569)"

This reverts commit 79b39f9655.

* Revert "fix(Core/Grid): Address bugs and performance issues introduced by visibility notifier implementation (#17480)"

This reverts commit 60e27511c5.

* Revert "fix(Core): GridCleanUpDelay Log (#17436)"

This reverts commit 90b16ca065.

* Revert "feat(Core/Grids): Implement visibility notifier (#15919)"

This reverts commit 2779833768.

src/server/scripts/Northrend/Ulduar/Ulduar/boss_algalon_the_observer.cpp

@@ -484,7 +484,6 @@ public:
 
             uint32 introDelay = 0;
             me->setActive(true);
-            me->SetFarVisible(true);
             me->SetInCombatWithZone();
             me->SetUnitFlag(UNIT_FLAG_NOT_SELECTABLE);
             me->SetImmuneToNPC(true);

src/server/scripts/Northrend/Ulduar/Ulduar/boss_razorscale.cpp

@@ -175,7 +175,6 @@ public:
         {
             me->SetDisableGravity(true);
             me->setActive(true);
-            me->SetFarVisible(true);
             Reset();
         }
 

src/server/scripts/Northrend/Ulduar/Ulduar/boss_thorim.cpp

@@ -517,7 +517,6 @@ public:
             if (m_pInstance && !_encounterFinished)
                 m_pInstance->SetData(TYPE_THORIM, IN_PROGRESS);
             me->setActive(true);
-            me->SetFarVisible(true);
             DisableThorim(true);
             me->CastSpell(me, SPELL_SHEATH_OF_LIGHTNING, true);
             //me->CastSpell(me, SPELL_TOUCH_OF_DOMINION, true);