umu -> umu-launcher: switch to npins & rename to umu-launcher #859

Job	Run time
check (NIXPKGS_ALLOW_INSECURE=1 nix flake check --accept-flake-config --impure) / nix	3m 17s
check (nix run nixpkgs#alejandra -- -c . -e ./npins) / nix	41s
build / build (faf-client-unstable) / nix	50s
build / build (faf-client) / nix	52s
build / build (proton-ge) / nix	29s
build / build (umu-launcher) / nix	1m 25s
build / build (wine-ge) / nix	1m 38s
build / build (wine-osu) / nix	1m 2s
build / build (wine-tkg) / nix	1m 47s
	12m 1s

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