Optimize Dockerfile for python environment

[GREENRAT-K405]

Changes I have made:

• Replaced jupyter/base-notebook (about 2 G.B.) with the official python:3.10-slim image (about 120 mb).
• Optimized layer Caching by changing the sequence, re-installation won't happen unnecessarily unless requirements.txt is modified.
• used apt & pip cleanup to prevent the cache from being permanently backed into the image.
• removed USER root declaration, as python slim images run as root by default, keeping the execution clean.

This fixes #334

[GREENRAT-K405]

@pradeeban , this should optimize python environment dockerfile by a lot!

[pradeeban]

We had plans to actively use Jupyter. Even FRI has an API for Jupyer, I believe. Anyway, we never really used it. Ok to proceed with your fix.