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/Serialize/Serializer.cpp

@@ -21,7 +21,7 @@
 
 #include "Common/Serialize/Serializer.h"
 #include "Common/Serialize/SerializeFuncs.h"
-#include "Common/FileUtil.h"
+#include "Common/File/FileUtil.h"
 #include "Common/StringUtils.h"
 
 PointerWrapSection PointerWrap::Section(const char *title, int ver) {