Fix current values being overridden.

At the beginning of a re-evaluation pass we mark all effective values as unset in order to signal that we've not yet found a value for them in the value frames. We do this in all cases except when they have a local value: in the case of a local value, the effective value _is_ the value and so value frames should only take effect when they're higher priority than the effective value. However when I added `SetCurrentValue` support, I neglected to change this logic to also take into account current values.

Fixes #10655
Fixes #10671

src/Avalonia.Base/PropertyStore/EffectiveValue.cs

@@ -54,9 +54,9 @@ namespace Avalonia.PropertyStore
         /// </remarks>
         public void BeginReevaluation(bool clearLocalValue = false)
         {
-            if (clearLocalValue || Priority != BindingPriority.LocalValue)
+            if (clearLocalValue || (Priority != BindingPriority.LocalValue && !IsOverridenCurrentValue))
                 Priority = BindingPriority.Unset;
-            if (clearLocalValue || BasePriority != BindingPriority.LocalValue)
+            if (clearLocalValue || (BasePriority != BindingPriority.LocalValue && !IsOverridenCurrentValue))
                 BasePriority = BindingPriority.Unset;
         }