Show section name in CI logs collapsible region
Problem to solve
Currently, in CI logs, it looks like the collapsible regions are placed randomly:
(screenshot of https://gitlab.com/gitlab-org/gitlab-ce/-/jobs/233462571)
This is also quite confusing using the new JSON job logs with Docker executor
For each start of the section, the Runner should write an informative line of what is going on to make it friendlier to the user.