Formatter: no_blank_line_before_class_docstring preview style #8888
Description
Implement the no_blank_lines_before_class_docstring as a preview style.
The new style aligns the docstring formatting between functions and classes.
class C:
"""The line above stays."""Gets reformatted to
class C:
"""The line above stays."""as it is already the case for functions.
Task: Copy over the test files, implement the new style behind a preview flag.