Refactored Keyboard Manager UI code and added unit tests for Keyboard Manager UI (#5718)

* Added tests for loading and saving remappings in the UI

* Added tests for ApplyRemappings methods

* Moved single key remap validation logic to separate method so that it can be tested

* Added tests for single key remap validation in UI

* Refactored shortcut validation code to be testable

* Added some shortcut validation tests

* Refactored code to be cleaner

* Added tests for action key and modifier key selection and formatted file

* Added tests for selecting None

* Added tests for selecting Null

* Added tests for WinL error

* Added CtrlAltDel tests

* Added tests for MapToSameKey

* Added tests for mapping repeated shortcut

* Fixed const correctness

* Clean up type names with type alias

* Clean up ValidateAndUpdateKeyBufferElement tests and tweak ValidateShortcutBufferElement signature

* Fixed bug when None selected

* Refactored one test as per test case framework

* Cleaned up more tests

* Cleaned up buffer validation tests

* Added tests for KBM Common Helpers and Shortcut

src/modules/keyboardmanager/ui/SingleKeyRemapControl.h

@@ -1,7 +1,6 @@
 #pragma once
 #include "KeyDropDownControl.h"
 #include <keyboardmanager/common/Shortcut.h>
-#include <variant>
 
 class KeyboardManagerState;
 namespace winrt::Windows::UI::Xaml
@@ -34,7 +33,7 @@ public:
     // Pointer to the keyboard manager state
     static KeyboardManagerState* keyboardManagerState;
     // Stores the current list of remappings
-    static std::vector<std::pair<std::vector<std::variant<DWORD, Shortcut>>, std::wstring>> singleKeyRemapBuffer;
+    static RemapBuffer singleKeyRemapBuffer;
 
     // constructor
     SingleKeyRemapControl(Grid table, const int colIndex);