[Perf] Set x:Load=false for StandardOperators

As a workaround for nventive/Uno#925 (binding to x:Load doesn't work), this improves start-up time when going directly to calculators other than Standard.

src/Calculator.Shared/Views/Calculator.xaml.cs

@@ -301,6 +301,11 @@ namespace CalculatorApp
 
         void OnIsStandardPropertyChanged(bool oldValue, bool newValue)
         {
+			if (newValue)
+			{
+				EnsureStandard();
+			}
+
             UpdateViewState();
             UpdatePanelViewState();
         }
@@ -430,6 +435,11 @@ namespace CalculatorApp
             }
         }
 
+		void EnsureStandard()
+		{
+			OpsPanel.EnsureStandardOps();
+		}
+
         void EnsureScientific()
         {
             OpsPanel.EnsureScientificOps();

src/Calculator.Shared/Views/OperatorsPanel.xaml

@@ -11,7 +11,7 @@
 	<Grid>
 		<!--Bind visibility as a workaround for nventive/Uno#925-->
 		<local:CalculatorStandardOperators x:Name="StandardOperators"
-																			 x:Load="{x:Bind Model.IsStandard, Mode=OneWay}"
+																			 x:Load="False"
 																			 IsEnabled="{x:Bind Model.IsStandard, Mode=OneWay}"
 																			 Visibility="{x:Bind Model.IsStandard, Mode=OneWay}"
 																			 TabIndex="17" />

src/Calculator.Shared/Views/OperatorsPanel.xaml.cs

@@ -88,6 +88,14 @@ namespace CalculatorApp
 			}
 		}
 
+		internal void EnsureStandardOps()
+		{
+			if (StandardOperators == null)
+			{
+				this.FindName("StandardOperators");
+			}
+		}
+
 		internal void EnsureScientificOps()
 		{
 			if (ScientificOperators == null)