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.

UI/RemoteISOScreen.cpp

@@ -27,9 +27,9 @@
 
 // TODO: For text align flags, probably shouldn't be in gfx_es2/...
 #include "gfx_es2/draw_buffer.h"
-#include "net/http_client.h"
-#include "net/resolve.h"
-#include "net/url.h"
+#include "Common/Net/HTTPClient.h"
+#include "Common/Net/Resolve.h"
+#include "Common/Net/URL.h"
 
 #include "Common/File/PathBrowser.h"
 #include "Common/Data/Format/JSONReader.h"