Implement no_blank_line_before_class_docstring preview style (#9154)

## Summary

This PR implements the `no_blank_line_before_class_docstring` preview
style.

## Test Plan

Update existing snapshots.

### Formatter ecosystem

`main`

| project | similarity index | total files | changed files |
|----------------|------------------:|------------------:|------------------:|
| cpython | 0.75804 | 1799 | 1648 |
| django | 0.99984 | 2772 | 34 |
| home-assistant | 0.99955 | 10596 | 213 |
| poetry | 0.99905 | 321 | 15 |
| transformers | 0.99967 | 2657 | 324 |
| twine | 1.00000 | 33 | 0 |
| typeshed | 0.99980 | 3669 | 18 |
| warehouse | 0.99976 | 654 | 14 |
| zulip | 0.99958 | 1459 | 36 |

`dhruv/no-blank-line-docstring`

| project | similarity index | total files | changed files |
|----------------|------------------:|------------------:|------------------:|
| cpython | 0.75804 | 1799 | 1648 |
| django | 0.99984 | 2772 | 34 |
| home-assistant | 0.99955 | 10596 | 213 |
| poetry | 0.99905 | 321 | 15 |
| transformers | 0.99967 | 2657 | 324 |
| twine | 1.00000 | 33 | 0 |
| typeshed | 0.99980 | 3669 | 18 |
| warehouse | 0.99976 | 654 | 14 |
| zulip | 0.99958 | 1459 | 36 |

fixes: #8888

crates/ruff_python_formatter/resources/test/fixtures/ruff/blank_line_before_class_docstring.options.json

@@ -0,0 +1,5 @@
+[
+  {
+    "preview": "enabled"
+  }
+]

crates/ruff_python_formatter/resources/test/fixtures/ruff/blank_line_before_class_docstring.py

@@ -0,0 +1,38 @@
+class NormalDocstring:
+
+    """This is a docstring."""
+
+
+class DocstringWithComment0:
+    # This is a comment
+    """This is a docstring."""
+
+
+class DocstringWithComment1:
+    # This is a comment
+
+    """This is a docstring."""
+
+
+class DocstringWithComment2:
+
+    # This is a comment
+    """This is a docstring."""
+
+
+class DocstringWithComment3:
+
+    # This is a comment
+
+    """This is a docstring."""
+
+
+class DocstringWithComment4:
+
+
+    # This is a comment
+
+
+    """This is a docstring."""
+
+