Use an empty vendored file system in Ruff #33200

Job	Run time
python package	1m 35s
cargo fmt	20s
Determine changes	9s
mkdocs	2m 56s
pre-commit	42s
cargo clippy	2m 5s
cargo test (wasm)	1m 34s
cargo build (release)	5m 25s
cargo build (msrv)	2m 59s
cargo test (linux)	2m 54s
cargo test (windows)	7m 17s
benchmarks	5m 28s
cargo fuzz	5m 13s
cargo shear	28s
test scripts	1m 14s
formatter instabilities and black similarity	3m 54s
Fuzz the parser	0s
test ruff-lsp	0s
ecosystem	0s
	44m 13s

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