Theoretical fix for some crashes (#16047)

Found this while looking through dumps for failure
`f544cf8e-1879-c59b-3f0b-1a364b92b974`. That's MSFT:45210947. (1% of our
1.19 crashes)

From the dump I looked at,

Looks like,

* we're on Windows 10
* We're refrigerating a window
* We are pumping the remaining XAML messages as we refrigerate
(`_pumpRemainingXamlMessages`)
* In there, we're finally getting the
`TerminalPage::_CompleteInitialization`
* that calls up to the `_root->Initialized` lambda set up in
`TerminalWindow::Initialize`
* There it tries to get the launch mode from the settings, and explodes.
Presumably _settings is null, but can't see in this dump.

so the window is closing before it's initialized.

When we `_warmWindow = std::move(_host->Refrigerate())`, we call
`AppHost::Refrigerate`, which will null out the TerminalWindow. So when
we're getting to `TerminalWindow::Initialize`, we're calling that on a
nullptr. That's the trick.

We need to revoke the internal Initialized callback. Which makes sense.
It's a lambda that binds _this_ 🤦

---

After more looking, it really doesn't _seem_ like the stacks that are
tracked in `f544cf8e-1879-c59b-3f0b-1a364b92b974` look like the same
stack that I was debugging, but this _is_ a realy issue regardless.

(cherry picked from commit 7073ec0)
Service-Card-Id: 90672654
Service-Version: 1.19

src/cascadia/TerminalApp/TerminalWindow.cpp

@@ -211,32 +211,7 @@ namespace winrt::TerminalApp::implementation
 
         _root->SetSettings(_settings, false); // We're on our UI thread right now, so this is safe
         _root->Loaded({ get_weak(), &TerminalWindow::_OnLoaded });
-
-        _root->Initialized([this](auto&&, auto&&) {
-            // GH#288 - When we finish initialization, if the user wanted us
-            // launched _fullscreen_, toggle fullscreen mode. This will make sure
-            // that the window size is _first_ set up as something sensible, so
-            // leaving fullscreen returns to a reasonable size.
-            const auto launchMode = this->GetLaunchMode();
-            if (_WindowProperties->IsQuakeWindow() || WI_IsFlagSet(launchMode, LaunchMode::FocusMode))
-            {
-                _root->SetFocusMode(true);
-            }
-
-            // The IslandWindow handles (creating) the maximized state
-            // we just want to record it here on the page as well.
-            if (WI_IsFlagSet(launchMode, LaunchMode::MaximizedMode))
-            {
-                _root->Maximized(true);
-            }
-
-            if (WI_IsFlagSet(launchMode, LaunchMode::FullscreenMode) && !_WindowProperties->IsQuakeWindow())
-            {
-                _root->SetFullscreen(true);
-            }
-
-            AppLogic::Current()->NotifyRootInitialized();
-        });
+        _root->Initialized({ get_weak(), &TerminalWindow::_pageInitialized });
         _root->Create();
 
         AppLogic::Current()->SettingsChanged({ get_weak(), &TerminalWindow::UpdateSettingsHandler });
@@ -255,6 +230,34 @@ namespace winrt::TerminalApp::implementation
             TraceLoggingKeyword(MICROSOFT_KEYWORD_MEASURES),
             TelemetryPrivacyDataTag(PDT_ProductAndServiceUsage));
     }
+
+    void TerminalWindow::_pageInitialized(const IInspectable&, const IInspectable&)
+    {
+        // GH#288 - When we finish initialization, if the user wanted us
+        // launched _fullscreen_, toggle fullscreen mode. This will make sure
+        // that the window size is _first_ set up as something sensible, so
+        // leaving fullscreen returns to a reasonable size.
+        const auto launchMode = this->GetLaunchMode();
+        if (_WindowProperties->IsQuakeWindow() || WI_IsFlagSet(launchMode, LaunchMode::FocusMode))
+        {
+            _root->SetFocusMode(true);
+        }
+
+        // The IslandWindow handles (creating) the maximized state
+        // we just want to record it here on the page as well.
+        if (WI_IsFlagSet(launchMode, LaunchMode::MaximizedMode))
+        {
+            _root->Maximized(true);
+        }
+
+        if (WI_IsFlagSet(launchMode, LaunchMode::FullscreenMode) && !_WindowProperties->IsQuakeWindow())
+        {
+            _root->SetFullscreen(true);
+        }
+
+        AppLogic::Current()->NotifyRootInitialized();
+    }
+
     void TerminalWindow::Quit()
     {
         if (_root)

src/cascadia/TerminalApp/TerminalWindow.h

@@ -202,6 +202,7 @@ namespace winrt::TerminalApp::implementation
 
         void _RefreshThemeRoutine();
         void _OnLoaded(const IInspectable& sender, const Windows::UI::Xaml::RoutedEventArgs& eventArgs);
+        void _pageInitialized(const IInspectable& sender, const IInspectable& eventArgs);
         void _OpenSettingsUI();
 
         winrt::Windows::Foundation::Collections::IVector<Microsoft::Terminal::Settings::Model::ActionAndArgs> _contentStringToActions(const winrt::hstring& content,