Fix a subset of existing lint issues

[peytondmurray]

This PR fixes a bunch of existing lint issues that were automatically fixed by ruff --fix, in preparation for merging #2251. I've ignored a bunch of rule violations, but marked them in ruff.toml so that they can be systematically re-enabled and the violations fixed one by one. The vast majority of these changes are:

• Removing useless whitespace at the end of lines
• Making sure the end of file contains a newline
• Removing unnecessary python 2/3 compatibility __future__ imports
• Import sorting
• Replacing calls to format() with f-strings, which are faster and more expressive

[peytondmurray]

Not really sure about the import/copybara check - I don't know what this check is. The Ubuntu CPU check is also not visible to me. Can someone confirm that it's okay if these are not passing?

[rtg0795]

@gharibian Would you mind taking a look at this and review.

[peytondmurray]

@gharibian Is there anything I can do to help get this merged? I'd really like to get this in so that the lint workflow can get unblocked.

[smokestacklightnin]

Closing as superseded by #4119