Refactor jet pointer and environment handling in Rust generation #1

Job	Run time
codespell	17s
build (haskell, ubuntu-latest, nixos-25.05)	24m 11s
build (c, ubuntu-latest, nixos-25.05)	1m 16s
build (c, macos-latest, nixos-25.05)	2m 35s
build (c, ubuntu-latest, nixpkgs-unstable)	1m 7s
build (haskell, macos-latest, nixos-25.05)	36m 43s
build (haskell, macos-latest, nixpkgs-unstable)	28m 19s
build (c, macos-latest, nixpkgs-unstable)	3m 10s
build (haskell, ubuntu-latest, nixpkgs-unstable)	24m 9s
	2h 1m 47s

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