Upgrade to Ubuntu 24.04 for our application

[humitos]

• Use Ubuntu 24.04 for our Docker images
• The application runs with Python 3.12 now
• Run tests with Python 3.12
• Update APT package names
• Install uv in the default directory ~/.local/bin
• Add uv to the PATH
• Create a virtualenv inside the Docker image for our application. --system option does not work anymore with the newer pip versions. It fails saying that we should install Python dependencies using system package.
• Upgrade Celery dependency to be compatible with Python 3.12
• The pickle error we used to see with Celery does not happen anymore with the newer version + py3.12
• Remove tzdata because it's installed automatically now

ToDo

• tests pass locally
• build a failed build that raises ConfigError without breaking
• build a success build
• tests pass in CircleCI
• update -ops to use Ubuntu 24.04
• build an AMI
• deploy one instance and run a build there
• do the same upgrade on .com

Notes

• All the Python commands inside the Docker container needs to be prefixed with uv run now. Example: uv run tox -e 312 or uv run django-admin and similars.

Related https://github.com/readthedocs/readthedocs-ops/issues/1496
Closes #12000

[humitos]

I deployed a web and a build instance and everything worked fine after some small updates. The build succeeded: https://app.readthedocs.org/projects/test-builds/builds/27242664/

This is last log line from the build task:

Feb 19 14:21:36 build-default-i-0a2edd075dcdce271 supervisord: build readthedocs[1456]: [info     ] Build finished.                [readthedocs.projects.tasks.builds:776] artifacts=['html', 'pdf'] build_id=27242664 builder=build-default-i-0a2edd075dcdce271 commit=None length=156 path_resolved=/home/docs/checkouts/readthedocs.org/user_builds/test-builds/checkouts/full-feature/.readthedocs.yaml project_slug=test-builds request_id=206e0526-3d8d-45f6-8bfc-1637a31f40ab success=True task_id=bba00d5b-329a-4a02-a8de-bdeeea640684 user_id=4890 version_slug=full-feature

[humitos]

I'm merging this so we can all start testing it locally. I will jump into .com now.