ruff_python_ast: Make `Singleton` `Copy` #37278

Job	Run time
cargo fmt	19s
Determine changes	12s
cargo build (release)	0s
mkdocs	2m 45s
pre-commit	44s
python package	1m 22s
benchmarks	5m 2s
cargo build (msrv)	3m 54s
cargo clippy	1m 44s
cargo fuzz build	0s
cargo shear	24s
cargo test (linux)	1m 44s
cargo test (linux, release)	3m 36s
cargo test (wasm)	1m 35s
cargo test (windows)	5m 19s
formatter instabilities and black similarity	3m 14s
test scripts	1m 0s
ecosystem	3m 59s
test ruff-lsp	40s
fuzz parser	6m 9s
	43m 42s

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