Core/Realms: Realmlist refactors

* Removed global realm variable from World and use RealmList everywhere
* Match auth build key with client version
* Restored allowedSecurityLevel checks for realmlist packet building
* Restored updating population field
Port From (https://github.com/TrinityCore/TrinityCore/commit/c4b710446d62c95eb8124175203fa5f394912594)

Source/Framework/Constants/Authentication/RealmConst.cs

@@ -7,6 +7,20 @@ namespace Framework.Constants
 {
     [Flags]
     public enum RealmFlags
+    {
+        None = 0x00,
+        VersionMismatch = 0x01,
+        Hidden = 0x02,
+        Tournament = 0x04,
+        VersionBelow = 0x08,
+        VersionAbove = 0x10,
+        MobileVersionMismatch = 0x20,
+        MobileVersionBelow = 0x40,
+        MobileVersionAbove = 0x80
+    }
+
+    [Flags]
+    public enum LegacyRealmFlags
     {
         None = 0x00,
         VersionMismatch = 0x01,
@@ -19,6 +33,18 @@ namespace Framework.Constants
         Full = 0x80
     }
 
+    public enum RealmPopulationState
+    {
+        Offline = 0,
+        Low = 1,
+        Medium = 2,
+        High = 3,
+        New = 4,
+        Recommended = 5,
+        Full = 6,
+        Locked = 7
+    }
+
     public enum RealmType
     {
         Normal = 0,