Ruff: prefer single quotes over double quotes

[adamjstewart]

I promise this is the single most controversial style change I will ever propose.

I hate double quotes. The only reason I've ever used double quotes is because black required them. Single quotes are better for the following reasons:

• I don't have to press the Shift key as often
• They are easier on the eyes, especially for short strings (in my opinion)
• Python repr defaults to single quotes (print(repr("hello world")) displays 'hello world')
• They don't have to be escaped in Jupyter Notebooks (yes, I edit those in vim)

Conversely, double quotes are better for the following reason:

• Single quote apostrophes are more common than double quotes in text

However, both black and ruff default to " when ' is in the string, and vice versa. So this decision only affects strings that contain neither.

We will want to add this PR commit to .git-blame-ignore-revs after merging so that git blame still works correctly.

psf/black#118 also contains some arguments for and against single and double quotes.