test: improve modularization

This improves debugging and experimenting by making it easy to compose fine-grained
scenarios that have specific tests and features enabled.

The VM test output now includes the subtest name and duration.

Remove the 'raise Exception()' hack for interactive mode.

Run 'banlist-and-restart' test before 'backups'. This speeds up the test
by avoiding an extra shutdown of all bitcoin-related services.

test/lib/test-lib.nix

@@ -0,0 +1,30 @@
+{ config, lib, ... }:
+with lib;
+{
+  options = {
+    test = {
+      noConnections = mkOption {
+        type = types.bool;
+        default = true;
+        description = ''
+          Whether services should be configured to not connect to external hosts.
+          This can silence some warnings while running the test in an offline environment.
+        '';
+      };
+      data = mkOption {
+        type = types.attrs;
+        default = {};
+        description = ''
+          Attrs that are available in the Python test script under the global
+          dictionary variable 'test_data'. The data is exported via JSON.
+        '';
+      };
+    };
+
+    tests = mkOption {
+      type = with types; attrsOf bool;
+      default = {};
+      description = "Python tests that should be run.";
+    };
+  };
+}