Use section name range for all section-related docstring diagnostics (#10740)
## Summary
We may not have had access to this in the past, but in short, if the
diagnostic is related to a specific section of a docstring, it seems
better to highlight the section (via the header) than the _entire_
docstring.
This should be completely compatible with existing `# noqa` since it's
always inside of a multi-line string anyway, and in such cases the `#
noqa` is always placed at the end of the multiline string.
Closes https://github.com/astral-sh/ruff/issues/10736.