ci: add unit test task to the CI

Description

This MR migrates the make test task into GitLab CI.

Related Issue

I started from this MR: !995 (closed)

Resolves #1005 (closed)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation
• Chore (Related to CI or Packaging to platforms)

Resources

• SSH Host Key Verification Failed inside GitLab CI - Stack Overflow

  • ssh-keyscan www.gitlab.com >> /.ssh/known_hosts

• bash - How to specify the private SSH-key to use when executing shell command on Git? - Stack Overflow
• Using SSH keys with GitLab CI/CD | GitLab