Update CommandPalette.cpp to ignore _filterTextChanged on TabSwitchMode (#16858)

As mentioned in #11146, when the "Next/Prev" command is executed from
the command line with a string in the search bar, this is setting always
the first tab.

When using the command "Next/Previous Tab" from the command line, we are
creating another tab (as if we are using the keyboard shortcut), and
this triggers the `_filterTextChanged` that resets the index to the
first item in because the current mode that it has.

This could be cause because, It seems that it detects as if we are
deleting the entered letter or creating an empty string, causing the
execution of the mentioned method and resetting its index to 0.

To avoid this, we are making sure that when this action is triggerd and
we are in the `TabSwitchMode`, we should ignore the following execution
of the method.

## Validation Steps Performed
I tested out the following scenarios:
1. Performing the action with the keyboard shorcut
2. Perfoming the action with an empty string
3. Performing the action with a string in the search bar.

Also validated with the current tests.

Closes #11146

(cherry picked from commit 806d5e2)
Service-Card-Id: 92139799
Service-Version: 1.19

Author: AlejandroBlanco2001

src/cascadia/TerminalApp/CommandPalette.cpp

@@ -843,6 +843,16 @@ namespace winrt::TerminalApp::implementation
     void CommandPalette::_filterTextChanged(const IInspectable& /*sender*/,
                                             const Windows::UI::Xaml::RoutedEventArgs& /*args*/)
     {
+        // When we are executing the _SelectNextTab in the TabManagement.cpp, this method
+        // is getting triggered because we set up the default value for that CommandPalette
+        // with an empty string. Therefore, to avoid the reset of the index when executing
+        // the Next/Prev tab command, we are skipping this execution.
+        // Check issue https://github.com/microsoft/terminal/issues/11146
+        if (_currentMode == CommandPaletteMode::TabSwitchMode)
+        {
+            return;
+        }
+
         if (_currentMode == CommandPaletteMode::CommandlineMode)
         {
             _evaluatePrefix();