Fix the CI actions, tests and pypi config

[EddyCMWF]

What happened?

• The unit-tests hang due to URLs being unreachable
• The Pypi release actions are very repetitive and inefficient
• The versioning for PyPi releases is not correctly configured (should not require manual setting)
• Testing on old versions of python

What are the steps to reproduce the bug?

Trigger the CI actions
Release a version

Version

0.2.4

Platform (OS and architecture)

NA

Relevant log output

No response

Accompanying data

No response

Organisation

No response