implement tapserver BBA on all platforms

This expands the tapserver BBA interface to be available on all platforms. tapserver itself is still macOS-only, but newserv (the PSO server) is not, and it can directly accept local and remote tapserver connections as well. This makes the tapserver interface potentially useful on all platforms.

Source/Core/DolphinQt/Settings/BroadbandAdapterSettingsDialog.h

@@ -15,6 +15,7 @@ public:
   {
     Ethernet,
     XLinkKai,
+    TapServer,
     BuiltIn
   };