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/Value/AoeHealValues.cpp

@@ -16,13 +16,13 @@ uint8 AoeHealValue::Calculate()
 
     float range = 0;
     if (qualifier == "low")
-        range = sPlayerbotAIConfig->lowHealth;
+        range = sPlayerbotAIConfig.lowHealth;
     else if (qualifier == "medium")
-        range = sPlayerbotAIConfig->mediumHealth;
+        range = sPlayerbotAIConfig.mediumHealth;
     else if (qualifier == "critical")
-        range = sPlayerbotAIConfig->criticalHealth;
+        range = sPlayerbotAIConfig.criticalHealth;
     else if (qualifier == "almost full")
-        range = sPlayerbotAIConfig->almostFullHealth;
+        range = sPlayerbotAIConfig.almostFullHealth;
 
     uint8 count = 0;
     Group::MemberSlotList const& groupSlot = group->GetMemberSlots();
@@ -32,7 +32,7 @@ uint8 AoeHealValue::Calculate()
         if (!player || !player->IsAlive())
             continue;
 
-        if (player->GetDistance(bot) >= sPlayerbotAIConfig->sightDistance)
+        if (player->GetDistance(bot) >= sPlayerbotAIConfig.sightDistance)
             continue;
 
         float percent = (static_cast<float>(player->GetHealth()) / player->GetMaxHealth()) * 100;