Implement IResolver (#442)

* Implement IResolver

- GetAddrInfo & GetNameInfo still need to be implemented.

* Address comments

* Use MakeError

Ryujinx.HLE/HOS/Services/Sfdnsres/GaiError.cs

@@ -0,0 +1,22 @@
+namespace Ryujinx.HLE.HOS.Services.Sfdnsres
+{
+    enum GaiError
+    {
+        Success,
+        AddressFamily,
+        Again,
+        BadFlags,
+        Fail,
+        Family,
+        Memory,
+        NoData,
+        NoName,
+        Service,
+        SocketType,
+        System,
+        BadHints,
+        Protocol,
+        Overflow,
+        Max,
+    }
+}