Format docstrings (#6452)

**Summary** Implement docstring formatting

**Test Plan** Matches black's `docstring.py` fixture exactly, added some
new cases for what is hard to debug with black and with what black
doesn't cover.

similarity index:

main:
zulip: 0.99702
django: 0.99784
warehouse: 0.99585
build: 0.75623
transformers: 0.99469
cpython: 0.75989
typeshed: 0.74853

this branch:

zulip: 0.99702
django: 0.99784
warehouse: 0.99585
build: 0.75623
transformers: 0.99464
cpython: 0.75517
typeshed: 0.74853

The regression in transformers is actually an improvement in a file they
don't format with black (they run `black examples tests src utils
setup.py conftest.py`, the difference is in hubconf.py). cpython doesn't
use black.

Closes #6196

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

@@ -0,0 +1,15 @@
+[
+  {
+    "indent_style": {
+      "Space": 4
+    }
+  },
+  {
+    "indent_style": {
+      "Space": 2
+    }
+  },
+  {
+    "indent_style": "Tab"
+  }
+]

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

@@ -0,0 +1,102 @@
+def single_line_backslashes1():
+  """ content\     """
+  return
+
+
+def single_line_backslashes2():
+  """ content\\     """
+  return
+
+
+def single_line_backslashes3():
+  """ content\\\     """
+  return
+
+
+def multiline_backslashes1():
+  """This is a docstring with
+  some lines of text\     """
+  return
+
+
+def multiline_backslashes2():
+  """This is a docstring with
+  some lines of text\\     """
+  return
+
+
+def multiline_backslashes3():
+  """This is a docstring with
+  some lines of text\\\     """
+  return
+
+
+def multiple_negatively_indented_docstring_lines():
+    """a
+ b
+  c
+   d
+    e
+    """
+
+
+def overindentend_docstring():
+    """a
+            over-indented
+    """
+
+
+def comment_before_docstring():
+    # don't lose this function comment ...
+    """Does nothing.
+
+    But it has comments
+    """  # ... neither lose this function comment
+
+
+class CommentBeforeDocstring():
+    # don't lose this class comment ...
+    """Empty class.
+
+    But it has comments
+    """  # ... neither lose this class comment
+
+
+class IndentMeSome:
+    def doc_string_without_linebreak_after_colon(self): """ This is somewhat strange
+         a
+      b
+         We format this a is the docstring had started properly indented on the next
+         line if the target indentation. This may we incorrect since source and target
+         indentation can be incorrect, but this is also an edge case.
+         """
+
+
+class IgnoreImplicitlyConcatenatedStrings:
+    """""" ""
+
+
+def docstring_that_ends_with_quote_and_a_line_break1():
+    """
+    he said "the news of my death have been greatly exaggerated"
+    """
+
+
+def docstring_that_ends_with_quote_and_a_line_break2():
+    """he said "the news of my death have been greatly exaggerated"
+    """
+
+
+def docstring_that_ends_with_quote_and_a_line_break3():
+    """he said "the news of my death have been greatly exaggerated"
+
+    """
+
+
+class TabbedIndent:
+	def tabbed_indent(self):
+		"""check for correct tabbed formatting
+		                            ^^^^^^^^^^
+		Normal indented line
+		  	- autor
+		"""