Format all attribute dot comments manually (#6825)

## Summary

This PR modifies our formatting of comments around the `.` in an
attribute. Specifically, the goal here is to avoid _reordering_
comments, and the net effect is that we generally leave comments
where-they-are when dealing with comments between around the dot (which
you can also think of as comments between attributes).

All comments around the dot are now treated as dangling and formatted
manually, with the exception of end-of-line or parenthesized comments on
the value, like those marked as trailing here, which remain trailing:

```python
(
    (
        a # trailing end-of-line
        # trailing own-line
    ) # dangling before dot end-of-line
    .b # trailing end-of-line
)
```

Closes https://github.com/astral-sh/ruff/issues/6823.

## Test Plan

`cargo test`

Before:

| project      | similarity index |
|--------------|------------------|
| cpython      | 0.76050          |
| django       | 0.99820          |
| transformers | 0.99800          |
| twine        | 0.99876          |
| typeshed     | 0.99953          |
| warehouse    | 0.99615          |
| zulip        | 0.99729          |

After:

| project      | similarity index |
|--------------|------------------|
| cpython      | 0.76050          |
| django       | 0.99820   |
| transformers | 0.99800          |
| twine        | 0.99876          |
| typeshed     | 0.99953          |
| warehouse    | 0.99615          |
| zulip        | 0.99729          |

crates/ruff_python_trivia/src/tokenizer.rs

@@ -19,6 +19,24 @@ pub fn first_non_trivia_token(offset: TextSize, code: &str) -> Option<SimpleToke
         .next()
 }
 
+/// Returns the only non-trivia, non-closing parenthesis token in `range`.
+///
+/// Includes debug assertions that the range only contains that single token.
+pub fn find_only_token_in_range(
+    range: TextRange,
+    token_kind: SimpleTokenKind,
+    code: &str,
+) -> SimpleToken {
+    let mut tokens = SimpleTokenizer::new(code, range)
+        .skip_trivia()
+        .skip_while(|token| token.kind == SimpleTokenKind::RParen);
+    let token = tokens.next().expect("Expected a token");
+    debug_assert_eq!(token.kind(), token_kind);
+    let mut tokens = tokens.skip_while(|token| token.kind == SimpleTokenKind::LParen);
+    debug_assert_eq!(tokens.next(), None);
+    token
+}
+
 /// Returns the number of newlines between `offset` and the first non whitespace character in the source code.
 pub fn lines_before(offset: TextSize, code: &str) -> u32 {
     let mut cursor = Cursor::new(&code[TextRange::up_to(offset)]);