DownloadManager: Always use Nintendo servers + additional streamlining

- Download manager now always uses Nintendo servers. Requires only a valid OTP and SEEPROM dump so you can use it in combination with a Pretendo setup even without a NNID
- Account drop down removed from download manager since it's not required
- Internally all our API requests now support overriding which service to use
- Drop support for act-url and ecs-url command line parameters. Usage of network_services.xml ("custom" option in the UI) is preferred

src/gui/TitleManager.h

@@ -8,6 +8,8 @@
 
 #include "Cemu/Tools/DownloadManager/DownloadManager.h"
 
+#define DOWNLOADMGR_HAS_ACCOUNT_DROPDOWN 0
+
 class wxCheckBox;
 class wxStaticText;
 class wxListEvent;