workspace: use node:test to replace mocha

test/entry.js

@@ -1,3 +1,6 @@
 process.env.CI = true;
+const version = process.versions.node.split('.');
+version.pop();
+if (+version.join('.') < 18.8) throw new Error('Tests only available in NodeJS>=18.8');
 require('hydrooj/bin/hydrooj');
 require('./main');