Add provider functions to provider.Interface with GRPC implementation (#1437)

Signed-off-by: Christian Mesh <christianmesh1@gmail.com>

internal/provider-simple-v6/provider.go

@@ -147,6 +147,10 @@ func (s simple) ReadDataSource(req providers.ReadDataSourceRequest) (resp provid
 	return resp
 }
 
+func (s simple) CallFunction(r providers.CallFunctionRequest) providers.CallFunctionResponse {
+	panic("Not Implemented")
+}
+
 func (s simple) Close() error {
 	return nil
 }