Core/Random: Changed random functions returning doubles to return floats

* They were all cast to float at use anyway
* Improves roll_chance_f performance (rand32() is now called internally by uniform_real_distribution once instead of twice)

src/server/game/Entities/Unit/Unit.cpp

@@ -1591,7 +1591,7 @@ static float GetArmorReduction(float armor, uint8 attackerLevel)
             discreteResistProbability[i] = std::max(0.5f - 2.5f * std::fabs(0.1f * i - averageResist), 0.0f);
     }
 
-    float roll = float(rand_norm());
+    float roll = rand_norm();
     float probabilitySum = 0.0f;
 
     uint32 resistance = 0;