ci: implement lint & Annoyatron

We want to run a linter on CI submission.

We also want to display nice error messages to the user. Thus, annoyatron is born.

The flow is as follows:

• a MR is submitted and triggers the 'lint' pipeline
• annoyatron gets pinged over https that an MR requires attention
• annoyatron starts running and waits until the MR's pipeline run succeeds or fails
• the lint jobs either succeeds or fails
• annoyatron notices the pipeline passed, and inspects its results to see if the lint pipeline failed or not.
• annoyatron posts a comment, if necessary