Do not redefine interfaces. (#67)

* Do not redefine interfaces.

* Improve code style, readability and performance after initial code review

* Implemented unit tests for the interface inheritance

* Cleaned up unit tests.

* Completely remove output helper.

tests/ProxyInterfaceSourceGeneratorTests/Source/Disposable/Explicit.cs

@@ -0,0 +1,25 @@
+namespace ProxyInterfaceSourceGeneratorTests.Source.Disposable
+{
+    public class Explicit : IDisposable, IUpdate<string>
+    {
+        string IUpdate<string>.Name => throw new NotSupportedException();
+
+        event EventHandler<string>? IUpdate<string>.Update
+        {
+            add
+            {
+                throw new NotSupportedException();
+            }
+
+            remove
+            {
+                throw new NotSupportedException();
+            }
+        }
+
+        void IDisposable.Dispose()
+        {
+            throw new NotSupportedException();
+        }
+    }
+}