Refactor model_servers/main.cc into a lib to ease reuse in custom servers that link in additional custom ops
Refactor model_servers/main.cc into a lib to ease reuse in custom servers
that link in additional custom ops

PiperOrigin-RevId: 200367387

penguin138/serving,tensorflow/serving,tensorflow/serving,penguin138/serving,penguin138/serving,tensorflow/serving,tensorflow/serving,penguin138/serving