Enforce Google-syle imports

[leandro-lucarella-frequenz]

What's needed?

To make sure we use Google-style imports.

Proposed solution

Add a pylint plugin to enforce this: https://pypi.org/project/pylint-google-style-guide-imports-enforcing/.

We also need to make sure we start writing modules and symbol names compatible with it, and eventually update old names too.

Use cases

No response

Alternatives and workarounds

No response

Additional context

Discussion:

• https://github.com/frequenz-floss/frequenz-sdk-python/discussions/209

[llucax]

I'm blocking this until we find a good package/module structure:

• 575