[engine] include lmi recommended entrypoint when model.py exists

[sindhuvahinis]

Description

Existing flow: If model.py exists in the model directory, without explicitly set by the user either in serving.properties or environment variables, then we take that as the entryPoint.

This PR:

• Still takes model.py as the entryPoint.
• But we also send the inferred built in handler as the recommended_entry_point to the python engine.
• In the python side, we check whether the given entry point has the handle or handler function name. If it does not exist, then we use the recommended_entry_point as the entry point

Tests:

• Manually tested in my ec2 machine.