Create and configure CI/CD pipelines

[rgallardone]

This PR creates the CI/CD pipelines for testing the changes, ensuring code quality and deploying the latest changes on the model and API to different services.

The tasks done on this PR are:

• Fix versions of some packages on test to avoid errors
• Fix bug on the model-test suite and modify the Makefile to accept the API URL as argument
• Create a small training script for loading the data, preprocessing it, training the model and persisting it
• Create the CI pipeline for assesing the code quality and format and running the model-test and api-test suites
• Create a GCP Service Account with the necessary permissions to deploy the API to Cloud Run
• Create a development environment in the Github Repository with configuration variables and secrets to authenticate with the created SA
• Create the CD pipeline for training the model, building the API image, deploying it to Cloud Run and running the stress tests

With these tasks completed, the Part 4 of the challenge is considered to be done.