Convert the repository to poetry

Description

This MR converts the repository to poetry instead of tito for easier tracking of the dependencies and easier safe usage. The CI is also fixed and adapted. As an optimization, a custom CI Docker image is produced.

RPM creation will be added in a subsequent MR.

Related Issue

How Has This Been Tested?

The repository can be used locally following the instruction in the developers' guide.

The CI is also fully working:

• A custom CI Docker image is produced on demand: https://gitlab.cern.ch/cmsgemonline/gem-online-analysis/container_registry/10566
• The documentation is published (manual job for master): https://cmsgemos.web.cern.ch/analysis/doc/
• Python packages will be released in the GitLab PyPi repository (manual job for master): will appear in https://gitlab.cern.ch/cmsgemonline/gem-online-analysis/-/packages

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.