chore: Allow Renovate to update npm tests

[haines]

The Renovate config:base preset includes the :ignoreModulesAndTests preset, which means that it's ignoring packages under npm/test.

This PR

• removes the config:base preset (which has been replaced by config:recommended anyway) and inlines the only preset included in it that we actually need (:dependencyDashboard);
• enables the configMigration setting so that we get PRs to keep the file up-to-date; and
• adds packageRules to configure the Node.js/npm updates.