Use treefmt and new build-env #1242

Job	Run time
build (ubuntu-latest, nix, false, false, 8107, nix-8107)	12m 26s
build (ubuntu-latest, stack, --stack-yaml stack-lts-18.28-lowerbound.yaml, false, false, 8107, st...	31m 4s
build (ubuntu-latest, nix, false, false, 902, nix-902)	12m 29s
build (ubuntu-latest, nix, false, false, 928, nix-928)	11m 28s
build (ubuntu-latest, nix, false, false, 948, nix-948)	10m 17s
build (ubuntu-latest, nix, false, false, 966, nix-966)	9m 49s
build (ubuntu-latest, nix, false, false, 984, nix-984)	9m 40s
build (ubuntu-latest, nix, true, false, 9101, nix-9101)	10m 2s
build (ubuntu-latest, cabal, false, false, 9121, cabal-9121)	29m 49s
build (macOS-latest, nix, true, false, 9101, nix-9101)	11m 48s
	2h 28m 52s

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