[FancyZones] Hold Ctrl to select any number of zones (#4850)

* Started work

* Did something, not yet sure that it works

* Sort of works

* Cleari highlighted zones when using Ctrl after leaving a monitor

* Remove unnecessary line

* Enhanced UX. Maybe refactor?

* Changed the logic behind zone selection when dragging

* Various fixups

src/modules/fancyzones/lib/GenericKeyHook.h

@@ -0,0 +1,62 @@
+#pragma once
+
+#include <functional>
+#include "pch.h"
+
+template<int... keys>
+class GenericKeyHook
+{
+public:
+
+    GenericKeyHook(std::function<void(bool)> extCallback)
+    {
+        callback = std::move(extCallback);
+    }
+
+    void enable()
+    {
+#if defined(DISABLE_LOWLEVEL_HOOKS_WHEN_DEBUGGED)
+        if (IsDebuggerPresent())
+        {
+            return;
+        }
+#endif
+        if (!hHook)
+        {
+            hHook = SetWindowsHookEx(WH_KEYBOARD_LL, GenericKeyHookProc, GetModuleHandle(NULL), 0);
+        }
+    }
+
+    void disable()
+    {
+        if (hHook)
+        {
+            UnhookWindowsHookEx(hHook);
+            hHook = NULL;
+            callback(false);
+        }
+    }
+
+private:
+    static HHOOK hHook;
+    static std::function<void(bool)> callback;
+
+    static LRESULT CALLBACK GenericKeyHookProc(int nCode, WPARAM wParam, LPARAM lParam)
+    {
+        if (nCode == HC_ACTION)
+        {
+            if (wParam == WM_KEYDOWN || wParam == WM_KEYUP)
+            {
+                PKBDLLHOOKSTRUCT kbdHookStruct = (PKBDLLHOOKSTRUCT)lParam;
+                if (((kbdHookStruct->vkCode == keys) || ...))
+                {
+                    callback(wParam == WM_KEYDOWN);
+                }
+            }
+        }
+        return CallNextHookEx(hHook, nCode, wParam, lParam);
+    }
+};
+
+typedef GenericKeyHook<VK_LSHIFT, VK_RSHIFT> ShiftKeyHook;
+typedef GenericKeyHook<VK_LCONTROL, VK_RCONTROL> CtrlKeyHook;