change builtin installer to upstream nix experimental #7275

Job	Run time
Test Flake Build	3m 6s
build-devbox (macos-13)	1m 40s
golangci-lint (macos-13)	6m 48s
Spell Check with Typos	6s
build-devbox (ubuntu-latest)	27s
golangci-lint (ubuntu-latest)	1m 58s
auto-nix-install (ubuntu-latest, false)	1m 46s
test (not-main, ubuntu-latest, project-tests-off, 2.12.0)	11m 17s
test (not-main, ubuntu-latest, project-tests-only, 2.30.2)	11m 8s
auto-nix-install (ubuntu-latest, true)	1m 42s
test (not-main, ubuntu-latest, project-tests-off, 2.30.2)	9m 9s
test (not-main, ubuntu-latest, project-tests-only, 2.19.2)	10m 4s
test-nix-versions (ubuntu-latest, 2.17.0)	1m 47s
auto-nix-install (macos-13, true)	5m 11s
test (not-main, ubuntu-latest, project-tests-only, 2.12.0)	10m 56s
test-nix-versions (ubuntu-latest, 2.19.2)	1m 46s
test (not-main, ubuntu-latest, project-tests-off, 2.19.2)	11m 28s
test-nix-versions (ubuntu-latest, 2.16.1)	2m 18s
test-nix-versions (ubuntu-latest, 2.15.1)	2m 9s
test-nix-versions (ubuntu-latest, 2.18.0)	1m 42s
test-nix-versions (macos-13, 2.16.1)	4m 45s
test-nix-versions (macos-13, 2.24.7)	4m 39s
auto-nix-install (macos-13, false)	4m 47s
test-nix-versions (macos-13, 2.18.0)	5m 38s
test-nix-versions (ubuntu-latest, 2.24.7)	1m 35s
test-nix-versions (macos-13, 2.17.0)	4m 17s
test-nix-versions (macos-13, 2.19.2)	4m 47s
test-nix-versions (macos-13, 2.15.1)	4m 59s
	2h 11m 55s

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