Replace magic-nix-cache-action

The `DeterminateSystems/magic-nix-cache-action` action has been [deprecated](https://determinate.systems/posts/magic-nix-cache-free-tier-eol/) and no longer works. This PR replaces it with the `nix-community/cache-nix-action` action, which is actively maintained. It also replaces the `DeterminateSystems/nix-installer-action` action with the `nixbuild/nix-quick-install-action` action, which is required for the cache action to work. The cache has been configured to restore based on the runner's OS and architecture, so it should work on any runner.