Request: Remove sequential blank lines in docstrings

I'd like a way to get rid of extraneous whitespace in docstrings.

Here's an example of a docstring with way too much whitespace:

```python
def cool_function(x: int) -> None:
"""
Do nothing.

Parameters
----------
x
Description of x.

Notes
-----
Hello.

There.

"""

```

I'd like ruff to format this down to:

```python
def cool_function(x: int) -> None:
"""
Do nothing.

Parameters
----------
x
Description of x.

Notes
-----
Hello.

There.

"""
```

On a related note, there is currently no way to make sure there is _no_ blank line after the last section (the opposite of `D413`). This would be a useful lint to have!

The issue names no files or tests. Start by locating Ruff's existing docstring formatting and D413 lint implementations, then inspect their test coverage; done means sequential blank lines are normalized and trailing blank-line behavior is defined and covered for the examples shown.

Written by the indexing model from the issue text.