Add code coverage reporting to the project

[RomuDeuxfois]

Description

Integrate Codecov into the project to collect, publish, and visualize code coverage metrics.

This includes:

• generating coverage reports during CI
• uploading coverage data to Codecov
• making coverage results easily accessible
• generate codecoverage on PRs like OpenAEV

[corinnekrych]

@guillaumejparis @RomuDeuxfois is it ok to close this one? If not please reopen :)

[RomuDeuxfois]

@corinnekrych why closing it ? We need to have a code coverage report on codecov
https://app.codecov.io/gh/OpenAEV-Platform