feat(checker): DB Migration Checker job for GitLab repos (#400)

Description

• prepare a CI Checker job for GitLab repos
• add checking script to run CI Checker sessions
• add a GitLab code provider
• build Docker image for the job template and configure CI

Related issue

#400 (closed)

Examples

akartasov/green-zone!1 (comment 1034791256)

How to install a CI Checker job in GitLab CI Pipeline

!565 (comment 1037258266)

Checklist

• MR description has been reviewed
• MR changes are functionally tested
• MR does NOT have text changes OR there are text changes and they have been reviewed
• MR does NOT have API/CLI changes OR there are API/CLI changes and they have been reviewed
• MR does NOT have UI changes OR there are UI changes and they have been reviewed

Closes #400 (closed)