Serve component

[hhsecond]

What does this PR do?

Introducing serve component. This allow users to pass the minimalistic things to serve their model under a work

class SimpleServer(L.app.components.serve.PythonServer):

    def setup(self):
        self._model = lambda x: x

    def predict(self, data):
        return self._model(data)


app = L.LightningApp(SimpleServer(port=7777))

Features missing are

• Create a UI that exposes API information (using the APIAccessFrontend component)
• Mulitple workers is out of scope

Fixes #<issue_number>

Does your PR introduce any breaking changes? If yes, please list them.

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Did you have fun?

Make sure you had fun coding 🙃

cc @Borda

[tchaton]

LGTM !

[ethanwharris]

LGTM 😃

[Borda]

Is this replacement for lightning-cloud?