Implement `no_blank_line_before_class_docstring` preview style #22782

Job	Run time
cargo fmt	15s
Determine changes	7s
pre-commit	42s
python package	1m 7s
mkdocs	2m 10s
cargo test (windows)	4m 46s
cargo test (linux)	3m 46s
cargo clippy	1m 57s
cargo test (wasm)	1m 11s
cargo fuzz	4m 27s
formatter instabilities and black similarity	3m 58s
cargo udeps	1m 47s
test scripts	1m 16s
benchmarks	7m 44s
test ruff-lsp	19s
ecosystem	4m 44s
	40m 16s

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