Move fileutil, net, image loaders, ui to Common. (#13506)

* Move and rename file_util/fd_util to Common/File/FileUtil and DirListing

Let's also move net while we're at it.

Move the ZIM/PNG loaders over to Common.

Move the UI framework into Common

iOS buildfix

* Buildfix

* Buildfixes

* Apple buildfix

* This typo again..

* UWP buildfix

* Fix build of PPSSPPQt, such as it is (it's not in good condition...)

* Guess what? Another buildfix.

Common/ArmCPUDetect.cpp

@@ -22,10 +22,11 @@
 #if PPSSPP_ARCH(ARM) || PPSSPP_ARCH(ARM64)
 
 #include <ctype.h>
-#include "Common.h"
-#include "CPUDetect.h"
-#include "StringUtils.h"
-#include "FileUtil.h"
+
+#include "Common/Common.h"
+#include "Common/CPUDetect.h"
+#include "Common/StringUtils.h"
+#include "Common/File/FileUtil.h"
 #include "Common/Data/Encoding/Utf8.h"
 
 #if PPSSPP_PLATFORM(WINDOWS)