Bump Docker images use for documentation to Alpine 3.19

[jnoordsij]

What does this PR do?

Update both Docker images for docs to use the latest Alpine version (3.19).
Given that in Alpine 3.19 Python's package directory is marked as externally managed, the docs image was updated to use a Python venv. The requirements file was updated accordingly, to no longer include unrelated system packages and bump a few (nested) dependencies. Dependency bumps were kept to a minimum, but updating them further might definitely be a good follow-up.

Motivation

While trying to debug docs failure job for #10664, I noticed:

• the image versions were using different versions, not being the latest
• dependencies for mkdocs were not installable locally using requirements.txt

This PR should solve both issues (albeit still not explaining the job failure 😓). It should also make Python/pip package installation more consistent, given that system installed packages are no longer used.

More

• Added/updated tests
• Added/updated documentation

Additional Notes

Also threw in a typo fix I still had in my diffs because I figured a separate PR would be too much of a thing for this.

[ldez]

The requirements.txt should contain the exhaustive list of dependencies.
We encounter several time dependency problems related to breaking changes, so all the dependencies should be locked.

[jnoordsij]

The requirements.txt should contain the exhaustive list of dependencies.

It does still. I assume the previous version included system installed packages that came with installing pip and/or python3-dev; I've now generated it to have all direct dependencies listed on top and then pip freeze-ing after installing those.