Fixed #7372: Setting "altGrAliasing" to "false" disables AltGr (#7400)

## Summary of the Pull Request

Previously, if `altGrAliasing` was disabled, all `Ctrl+Alt` combinations were considered to be aliases of `AltGr` including `AltGr` itself and thus considered as key and not character events. But `AltGr` should not be treated as an alias of itself of course, as that prevents one from entering `AltGr` combinations entirely.

## PR Checklist
* [x] Closes #7372
* [x] CLA signed. If not, go over [here](https://cla.opensource.microsoft.com/microsoft/Terminal) and sign the CLA
* [x] Tests added/passed
* [ ] Documentation updated. If checked, please file a pull request on [our docs repo](https://github.com/MicrosoftDocs/terminal) and link it here: #xxx
* [ ] Schema updated.
* [ ] I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #xxx

## Validation Steps Performed

* Activate a German keyboard layout
* Run `showkey -a` in WSL
* **Ensure** that `AltGr+Q` produces `@`
* **Ensure** that `Ctrl+Alt+Q` produces `@`
* Disable `altGrAliasing`
* **Ensure** that `AltGr+Q` produces `@`
* **Ensure** that `Ctrl+Alt+Q` produces `^[^Q`

(cherry picked from commit ac310d9)

src/cascadia/TerminalCore/Terminal.cpp

@@ -457,7 +457,6 @@ bool Terminal::SendKeyEvent(const WORD vkey,
     }
 
     const auto isAltOnlyPressed = states.IsAltPressed() && !states.IsCtrlPressed();
-    const auto isSuppressedAltGrAlias = !_altGrAliasing && states.IsAltPressed() && states.IsCtrlPressed();
 
     // DON'T manually handle Alt+Space - the system will use this to bring up
     // the system menu for restore, min/maximize, size, move, close.
@@ -477,6 +476,7 @@ bool Terminal::SendKeyEvent(const WORD vkey,
     // as TerminalInput::HandleKey will then fall back to using the vkey which
     // is the underlying ASCII character (e.g. A-Z) on the keyboard in our case.
     // See GH#5525/GH#6211 for more details
+    const auto isSuppressedAltGrAlias = !_altGrAliasing && states.IsAltPressed() && states.IsCtrlPressed() && !states.IsAltGrPressed();
     const auto ch = isSuppressedAltGrAlias ? UNICODE_NULL : _CharacterFromKeyEvent(vkey, scanCode, states);
 
     // Delegate it to the character event handler if this key event can be