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.

Core/FileLoaders/DiskCachingFileLoader.cpp

@@ -15,17 +15,18 @@
 // Official git repository and contact information can be found at
 // https://github.com/hrydgard/ppsspp and http://www.ppsspp.org/.
 
+#include "ppsspp_config.h"
+
 #include <algorithm>
 #include <cstddef>
 #include <set>
 #include <mutex>
 #include <cstring>
 
-#include "ppsspp_config.h"
-#include "file/file_util.h"
 #include "Common/Data/Encoding/Utf8.h"
 #include "Common/File/DiskFree.h"
-#include "Common/FileUtil.h"
+#include "Common/File/DirListing.h"
+#include "Common/File/FileUtil.h"
 #include "Common/Log.h"
 #include "Common/CommonWindows.h"
 #include "Core/FileLoaders/DiskCachingFileLoader.h"