checks: move all tests to the test flake #1368

Job	Run time
examples-darwin	3m 12s
tests (https://nixos.org/nix/install)	2m 44s
examples-linux (alt-registry)	1m 36s
tests (https://releases.nixos.org/nix/nix-2.24.10/install, --override-input nixpkgs $(./ci/ref-fr...	23m 48s
lints	58s
examples-linux (build-std)	1m 32s
examples-linux (cross-musl)	1m 31s
examples-linux (cross-rust-overlay)	1m 31s
examples-linux (cross-windows)	1m 30s
examples-linux (custom-toolchain)	1m 30s
examples-linux (end-to-end-testing)	1m 31s
examples-linux (quick-start)	1m 30s
examples-linux (quick-start-simple)	1m 29s
examples-linux (quick-start-workspace)	1m 31s
examples-linux (sqlx)	1m 29s
examples-linux (trunk-workspace)	1m 32s
examples-linux (trunk)	1m 31s
all systems go	0s
	50m 25s

Provide feedback