Add some logging regarding command palette usage (#6821)

## Summary of the Pull Request

Pretty straightforward. Logs three scenarios:
* The user opened the command palette (and which mode it was opened in)
* The user ran a command from the palette
* The user dismissed the palette without running an action.

We discussed this in team sync yesterday.

## PR Checklist
* [x] I work here
* [n/a] Requires documentation to be updated

src/cascadia/TerminalApp/CommandPalette.cpp

@@ -41,11 +41,19 @@ namespace winrt::TerminalApp::implementation
             {
                 _searchBox().Focus(FocusState::Programmatic);
                 _filteredActionsView().SelectedIndex(0);
+
+                TraceLoggingWrite(
+                    g_hTerminalAppProvider, // handle to TerminalApp tracelogging provider
+                    "CommandPaletteOpened",
+                    TraceLoggingDescription("Event emitted when the Command Palette is opened"),
+                    TraceLoggingWideString(L"Action", "Mode", "which mode the palette was opened in"),
+                    TraceLoggingKeyword(MICROSOFT_KEYWORD_MEASURES),
+                    TelemetryPrivacyDataTag(PDT_ProductAndServicePerformance));
             }
             else
             {
                 // Raise an event to return control to the Terminal.
-                _close();
+                _dismissPalette();
             }
         });
     }
@@ -101,12 +109,7 @@ namespace winrt::TerminalApp::implementation
 
             if (const auto selectedItem = _filteredActionsView().SelectedItem())
             {
-                if (const auto data = selectedItem.try_as<Command>())
-                {
-                    const auto actionAndArgs = data.Action();
-                    _dispatch.DoAction(actionAndArgs);
-                    _close();
-                }
+                _dispatchCommand(selectedItem.try_as<Command>());
             }
 
             e.Handled(true);
@@ -116,7 +119,7 @@ namespace winrt::TerminalApp::implementation
             // Action Mode: Dismiss the palette if the text is empty, otherwise clear the search string.
             if (_searchBox().Text().empty())
             {
-                _close();
+                _dismissPalette();
             }
             else
             {
@@ -138,7 +141,7 @@ namespace winrt::TerminalApp::implementation
     void CommandPalette::_rootPointerPressed(Windows::Foundation::IInspectable const& /*sender*/,
                                              Windows::UI::Xaml::Input::PointerRoutedEventArgs const& /*e*/)
     {
-        _close();
+        _dismissPalette();
     }
 
     // Method Description:
@@ -166,14 +169,55 @@ namespace winrt::TerminalApp::implementation
     void CommandPalette::_listItemClicked(Windows::Foundation::IInspectable const& /*sender*/,
                                           Windows::UI::Xaml::Controls::ItemClickEventArgs const& e)
     {
-        if (auto command{ e.ClickedItem().try_as<TerminalApp::Command>() })
+        _dispatchCommand(e.ClickedItem().try_as<TerminalApp::Command>());
+    }
+
+    // Method Description:
+    // - Helper method for retrieving the action from a command the user
+    //   selected, and dispatching that command. Also fires a tracelogging event
+    //   indicating that the user successfully found the action they were
+    //   looking for.
+    // Arguments:
+    // - command: the Command to dispatch. This might be null.
+    // Return Value:
+    // - <none>
+    void CommandPalette::_dispatchCommand(const TerminalApp::Command& command)
+    {
+        if (command)
         {
             const auto actionAndArgs = command.Action();
             _dispatch.DoAction(actionAndArgs);
             _close();
+
+            TraceLoggingWrite(
+                g_hTerminalAppProvider, // handle to TerminalApp tracelogging provider
+                "CommandPaletteDispatchedAction",
+                TraceLoggingDescription("Event emitted when the user selects an action in the Command Palette"),
+                TraceLoggingKeyword(MICROSOFT_KEYWORD_MEASURES),
+                TelemetryPrivacyDataTag(PDT_ProductAndServicePerformance));
         }
     }
 
+    // Method Description:
+    // - Helper method for closing the command palette, when the user has _not_
+    //   selected an action. Also fires a tracelogging event indicating that the
+    //   user closed the palette without running a command.
+    // Arguments:
+    // - <none>
+    // Return Value:
+    // - <none>
+    void CommandPalette::_dismissPalette()
+    {
+        _close();
+
+        TraceLoggingWrite(
+            g_hTerminalAppProvider, // handle to TerminalApp tracelogging provider
+            "CommandPaletteDismissed",
+            TraceLoggingDescription("Event emitted when the user dismisses the Command Palette without selecting an action"),
+            TraceLoggingKeyword(MICROSOFT_KEYWORD_MEASURES),
+            TelemetryPrivacyDataTag(PDT_ProductAndServicePerformance));
+    }
+
     // Method Description:
     // - Event handler for when the text in the input box changes. In Action
     //   Mode, we'll update the list of displayed commands, and select the first one.

src/cascadia/TerminalApp/CommandPalette.h

@@ -39,6 +39,10 @@ namespace winrt::TerminalApp::implementation
         void _updateFilteredActions();
         static int _getWeight(const winrt::hstring& searchText, const winrt::hstring& name);
         void _close();
+
+        void _dispatchCommand(const TerminalApp::Command& command);
+
+        void _dismissPalette();
     };
 }