Remove duplicate oneOf schemas during pre-processing #592

Job	Run time
Build Rust (samples/client/others/rust/)	32s
Build Rust (samples/server/petstore/rust-axum/)	54s
Build Rust (samples/client/petstore/rust/)	53s
Build Rust (samples/server/petstore/rust-server/)	2m 24s
	4m 43s

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