Rust

xtask: fix nixfmt + update Nix flake + fix CI #6517

Job	Run time
Integration Test (AArch64)	1m 11s
Integration Test (x86_64)	1m 18s
Unit + Doc Tests (Miri)	1m 9s
Build Standard Binary (nightly)	25s
Nightly (build, test, doc)	1m 38s
Integration Test (IA-32)	1m 25s
Unit + Doc Tests	46s
Integration Test (x86_64 Windows)	3m 32s
Build (stable MSRV)	39s
Build (uefi-raw MSRV)	39s
Test Coverage	41s
Build (feature permutations)	3m 51s
	17m 14s

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