.NET Core 3.0 is here! (#784)

* .NET Core 3.0 is here!

* Remove IMemoryManager.cs and its references.

* Add T Math/F.FusedMultiplyAdd(T, T, T). Nits.

* Nit.

* Update appveyor.yml

* Revert "Resolve Visual Studio build issues"

This reverts commit 1772128ce0.

* Update SvcTable.cs

Ryujinx.Graphics/Graphics3d/Texture/TextureHelper.cs

@@ -38,7 +38,7 @@ namespace Ryujinx.Graphics.Texture
             }
         }
 
-        public static (IMemoryManager Memory, long Position) GetMemoryAndPosition(
+        public static (MemoryManager Memory, long Position) GetMemoryAndPosition(
             IMemory memory,
             long    position)
         {
@@ -47,7 +47,7 @@ namespace Ryujinx.Graphics.Texture
                 return (vmm.Memory, vmm.GetPhysicalAddress(position));
             }
 
-            return ((IMemoryManager)memory, position);
+            return ((MemoryManager)memory, position);
         }
     }
 }