feat (checker): run DB Migration Checker with GitLab CI/CD

Goal

Automatically checks DB migrations with GitLab CI/CD

TODO / How to implement

• create a job template to run CI Checker with GitLab CI/CD
  • copy functions from the GitHub Actions jobs (https://github.com/postgres-ai/dle-github-actions)
  • automatically publish CI Checker summary in MR
• describe ways to install template to a GitLab CI/CD pipeline

Acceptance criteria

DLE GitLab CI/CD jobs automatically checks DB migrations and publishes results