Improper singletons migration to clean Meyer's singletons (cherry-pick) (#2082)

# Pull Request

- Applies the clean and corrected singletons, Meyer pattern. (cherry
picked from @SmashingQuasar )

Testing by just playing the game in various ways. Been tested by myself
@Celandriel and @SmashingQuasar
---

## Complexity & Impact

- Does this change add new decision branches?
    - [x] No
    - [ ] Yes (**explain below**)

- Does this change increase per-bot or per-tick processing?
    - [x] No
    - [ ] Yes (**describe and justify impact**)

- Could this logic scale poorly under load?
    - [x] No
    - [ ] Yes (**explain why**)

---

## Defaults & Configuration

- Does this change modify default bot behavior?
    - [x] No
    - [ ] Yes (**explain why**)

---

## AI Assistance

- Was AI assistance (e.g. ChatGPT or similar tools) used while working
on this change?
    - [x] No
    - [ ] Yes (**explain below**)
---

## Final Checklist

- [x] Stability is not compromised
- [x] Performance impact is understood, tested, and acceptable
- [x] Added logic complexity is justified and explained
- [x] Documentation updated if needed

---

## Notes for Reviewers

Anything that significantly improves realism at the cost of stability or
performance should be carefully discussed
before merging.

---------

Co-authored-by: Nicolas Lebacq <nicolas.cordier@outlook.com>
Co-authored-by: Keleborn <22352763+Celandriel@users.noreply.github.com>

src/Ai/Base/Actions/RevealGatheringItemAction.cpp

@@ -20,16 +20,16 @@ bool RevealGatheringItemAction::Execute(Event event)
         return false;
 
     std::list<GameObject*> targets;
-    AnyGameObjectInObjectRangeCheck u_check(bot, sPlayerbotAIConfig->grindDistance);
+    AnyGameObjectInObjectRangeCheck u_check(bot, sPlayerbotAIConfig.grindDistance);
     Acore::GameObjectListSearcher<AnyGameObjectInObjectRangeCheck> searcher(bot, targets, u_check);
-    Cell::VisitObjects(bot, searcher, sPlayerbotAIConfig->reactDistance);
+    Cell::VisitObjects(bot, searcher, sPlayerbotAIConfig.reactDistance);
 
     std::vector<GameObject*> result;
     for (GameObject* go : targets)
     {
         if (!go || !go->isSpawned() ||
-            sServerFacade->IsDistanceLessOrEqualThan(sServerFacade->GetDistance2d(bot, go),
-                                                     sPlayerbotAIConfig->lootDistance))
+            ServerFacade::instance().IsDistanceLessOrEqualThan(ServerFacade::instance().GetDistance2d(bot, go),
+                                                     sPlayerbotAIConfig.lootDistance))
             continue;
 
         if (LockEntry const* lockInfo = sLockStore.LookupEntry(go->GetGOInfo()->GetLockId()))