Install docker CLI in test jobs instead of Python in ci-runner

Fix test job failures by using the ci-runner image (Alpine) which has
the necessary tools (postgresql16-client, py3-psycopg2, curl) instead
of overriding to ci-base-image (Ubuntu) which lacks these packages.

Changes:
- docker/ci/Dockerfile: Add curl and py3-psycopg2 to ci-runner
- .gitlab-ci.yml: Remove image overrides from regression-test,
  performance-test, and pattern-test so they use ci-runner

This fixes:
- psql: command not found (regression-test)
- ModuleNotFoundError: No module named 'psycopg2' (performance-test)
- curl connectivity issues in DinD