Rust

xtask: fix nixfmt + update Nix flake + fix CI #6519

Job	Run time
Integration Test (x86_64)	1m 35s
Integration Test (AArch64)	1m 11s
Build (feature permutations)	3m 52s
Integration Test (IA-32)	1m 33s
Test Coverage	43s
Build Standard Binary (nightly)	25s
Integration Test (x86_64 Windows)	3m 24s
Build (uefi-raw MSRV)	36s
Build (stable MSRV)	39s
Nightly (build, test, doc)	1m 48s
Unit + Doc Tests (Miri)	1m 13s
Unit + Doc Tests	50s
	17m 49s

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