chore(tests): bump the postgres version used in CI (#6763)

* bump the postgress version used in CI and fix the tests that broke

* sort Grants by raw grant string rather than GrantStrings

* trigger ci

testing/dbtest/docker/Dockerfile.18-alpine

@@ -0,0 +1,7 @@
+FROM postgres:18-alpine
+
+ADD init-db.sh /docker-entrypoint-initdb.d/00-init-db.sh
+ADD restore-benchmark-dumps.sh /docker-entrypoint-initdb.d/01-restore-benchmark-dumps.sh
+ADD postgresql.conf /etc/postgresql/postgresql.conf
+
+CMD ["postgres", "-c", "config_file=/etc/postgresql/postgresql.conf"]