Generalize ReagentUnit into FixedPoint2 and use it for damage calculations (#5151)

* Damage units

* sum ext method

Content.Client/MedicalScanner/UI/MedicalScannerWindow.xaml.cs

@@ -9,6 +9,7 @@ using Robust.Shared.Localization;
 using Robust.Shared.Prototypes;
 using static Content.Shared.MedicalScanner.SharedMedicalScannerComponent;
 using Content.Shared.Damage.Prototypes;
+using Content.Shared.FixedPoint;
 using Robust.Client.AutoGenerated;
 using Robust.Client.UserInterface.XAML;
 
@@ -39,6 +40,7 @@ namespace Content.Client.MedicalScanner.UI
                 text.Append($"{Loc.GetString("medical-scanner-window-entity-health-text", ("entityName", entity.Name))}\n");
 
                 var totalDamage = state.DamagePerType.Values.Sum();
+
                 text.Append($"{Loc.GetString("medical-scanner-window-entity-damage-total-text", ("amount", totalDamage))}\n");
 
                 HashSet<string> shownTypes = new();