* ci: try nix-community/cache-nix-action * ci: add cache-id param to setup-nix action * ci: tidy up cache keys for non-nix jobs * ci: merge-nix-caches-linux job * ci: merge caches other way around * ci: reduce number of caches Should prevent disk overflow * ci: change cache id prefix for merge * ci: comment out cache merging job * ci: revert cache id prefix * ci: setup-nix: use latest cache-nix-action Among others, makes action logs look more tidy (see https://github.com/nix-community/cache-nix-action/commit/17d19d3d8be918757589635bc1a6830be0b129d2) * ci: use test-pg cache key for loadtest