Rule to enforce import module only

The google style guide recommends importing modules only. https://google.github.io/styleguide/pyguide.html#22-imports. It would be great if there’s a rule to enforce that.

Start with the Google Python Style Guide's imports section and inspect Ruff's existing import-related rules and tests to find the relevant rule entry points. Define which imports violate the module-only requirement, then add coverage showing that the rule reports those cases without rejecting permitted imports.

Written by the indexing model from the issue text.