Common/CommonFuncs: Remove now-unneccessary ArraySize function

Since C++17, non-member std::size() is present in the standard library
which also operates on regular C arrays. Given that, we can just replace
usages of ArraySize with that where applicable.

In many cases, we can just change the actual C array ArraySize() was
called on into a std::array and just use its .size() member function
instead.

In some other cases, we can collapse the loops they were used in, into a
ranged-for loop, eliminating the need for en explicit bounds query.

Source/Core/VideoBackends/D3D12/DXContext.h

@@ -3,16 +3,17 @@
 // Refer to the license.txt file included.
 
 #pragma once
+
+#include <array>
+#include <functional>
+#include <map>
+
 #include "Common/CommonTypes.h"
 #include "VideoBackends/D3D12/Common.h"
 #include "VideoBackends/D3D12/DescriptorAllocator.h"
 #include "VideoBackends/D3D12/DescriptorHeapManager.h"
 #include "VideoBackends/D3D12/StreamBuffer.h"
 
-#include <array>
-#include <functional>
-#include <map>
-
 struct IDXGIFactory2;
 
 namespace DX12