Apply code style standards systematically e.g. with black

[sadielbartholomew]

Currently the codebase does not conform to PEP8 (and aligned) style conventions which are standard for Python code, for example it makes heavy use of old-style string formatting and has a large amount of trailing whitespace.

To avoid spending unnecessary time and effort to conform by such formatting, we should use a tool like black which will auto-format in a precise and absolute way as an extension of PEP8.

We can then use linters including pre-commit hooks to ensure that the style continues to abide by those standards (amongst other verifications).

[sadielbartholomew]

As part of this, we should tidy import order with the isort tool.

[sadielbartholomew]

I am hearing lots of good things about ruff, especially from those in the RSE community, so will probably go with that when I get around to doing this.

[sadielbartholomew]

Since cf-python uses black at present (my choice from a while back), I will go with that instead of ruff for now. But we can always update that later for both libraries, in sync.