Switch to MUX:CommandBarFlyout in XAML Islands proofing menu

This fixes the broken keyboard navigation in an islands app, however it
can cause a crash when using WinUI 2.6 (but is fixed in WinUI 2.7).

Closes microsoft#8306

Author: jonthysell

vnext/Microsoft.ReactNative/Utils/XamlIslandUtils.cpp

@@ -30,9 +30,9 @@ struct CustomAppBarButton : xaml::Controls::AppBarButtonT<CustomAppBarButton> {
   }
 };
 
-void FixProofingMenuCrashForXamlIsland(xaml::Controls::TextCommandBarFlyout const &flyout) {
+void FixProofingMenuCrashForXamlIsland(xaml::Controls::Primitives::FlyoutBase const &flyout) {
   flyout.Opening([](winrt::IInspectable const &sender, auto &&) {
-    const auto &flyout = sender.as<xaml::Controls::TextCommandBarFlyout>();
+    const auto &flyout = sender.as<winrt::Microsoft::UI::Xaml::Controls::TextCommandBarFlyout>();
     if (const auto &textBox = flyout.Target().try_as<xaml::Controls::TextBox>()) {
       const auto &commands = flyout.SecondaryCommands();
       for (uint32_t i = 0; i < commands.Size(); ++i) {

vnext/Microsoft.ReactNative/Utils/XamlIslandUtils.h

@@ -8,9 +8,11 @@
 #include <UI.Xaml.Controls.Primitives.h>
 #include <UI.Xaml.Controls.h>
 
+#include <winrt/Microsoft.UI.Xaml.Controls.h>
+
 namespace Microsoft::ReactNative {
 
-void FixProofingMenuCrashForXamlIsland(xaml::Controls::TextCommandBarFlyout const &flyout);
+void FixProofingMenuCrashForXamlIsland(xaml::Controls::Primitives::FlyoutBase const &flyout);
 
 template <typename T>
 inline void EnsureUniqueTextFlyoutForXamlIsland(T const &textView) {
@@ -19,7 +21,7 @@ inline void EnsureUniqueTextFlyoutForXamlIsland(T const &textView) {
   // to show the flyout on other windows cause the first window to get focus.
   // https://github.com/microsoft/microsoft-ui-xaml/issues/5341
   if (IsXamlIsland()) {
-    xaml::Controls::TextCommandBarFlyout flyout;
+    winrt::Microsoft::UI::Xaml::Controls::TextCommandBarFlyout flyout;
     flyout.Placement(xaml::Controls::Primitives::FlyoutPlacementMode::BottomEdgeAlignedLeft);
 
     // This works around a XAML Islands bug where the Proofing sub-menu for